* Protect Network from zero and negative mass values

Fix for #3133

Option-field 'node.mass` must be >= 0.
Checks have been added at the nodes level, for both nodes-global and nodes specific options.
In addition, an internal check has been added for `NodeHandler.defaultOptions`.

The documentation has been adjusted for this change.

* Fix whitespace

* Prevent crashes from invalid id's in `Clustering.findNode()`

Fix for #3163

- Added safeguards in said method, to prevent exceptions happening when invalid id's are passed in.
- Adjusted documentation for said method
- Added notes to flag unused methods in `Clustering.js`

* Removed incorrect NOTE-comments from methods that are indeed used

Currently `align` is only available as a global timeline configuration
option. This change allows overriding alignment on a per-item basis.

* Added param 'direction' to Network.getConnectedNodes()

* Redo commit - Network.js does not need to change

Awesome work! Thanks again!

* Add 'showTooltips' timeline option

* Only show timeline popup if option showTooltips is true

* Add 'showTooltips' option to timeline docs

* Add tooltips disabled timeline example

Sorry for the delay on this... It took me a while to confirm this PR again. I don;t know why I didn't merge it at the time I reviewed it. Looks great to me!

* mouseup and mousedown events

* Fix error

* Add Gitter badge (#2179)

* do not generate source-maps in distribution version

* add 'dist' folder for deployment

* added Badges

* added codeclimate badge

* added @Tooa to the support team

* added badges from isitmaintained.com (#2517)

* do not ignore dist and test folders in master

* generated dist files for v4.18.0

* generated dist files for v4.18.1

* Cheap fix for bug #2795

* Update to PR #2826 to use newline format

* changed to v4.18.1-SNAPSHOT

* chore(docs): general improvements (#2652)

* removed NOTICE file

* updated license date range to include 2017

* chore(docs): updated support team members

* chore: updated dependencies and devDependencies (#2649)

* Fixes instanceof Object statements for objects from other windows and iFrames. (#2631)

* Replaces instanceof Object checks with typeof to prevent cross tab issues.

* Adds missing space.

* chore: removed google-analytics from all examples (#2670)

* chore(docs): Add note that PRs should be submitted against the `develop` branch (#2623)

Related to: https://github.com/almende/vis/pull/2618
Related to: https://github.com/almende/vis/pull/2620

* feat(timeline): Change setCustomTimeTitle title parameter to be a string or a function (#2611)

* change setCustomTimeTitle title parameter, Now could be an string or a function
* Fixed indent and spacing

* feat(timeline): refactor tooltip to only use one dom-element (#2662)

* feat(network): Allow for image nodes to have a selected or broken image (#2601)

* feat(tests): run mocha tests in travis ci (#2687)

* Added showX(YZ)Axis options to Graph3d (#2686)

* Added showX(YZ)Axis to Graph3d

* Added show_Axis options to docs and playground example

* Resolved merge conflict

* Added show_Axis options to docs and playground example

* fix(build): use babel version compatible with webpack@1.14 (#2693)

fixes #2685

* feat(docs): use babel preset2015 for custom builds (#2678)

* add link to a mentioned example (#2709)

* chore(lint): added support for eslint (#2695)

* Trivial typo fix in how_to_help doc. (#2714)

* fix(timeline): #2598 Flickering onUpdateTimeTooltip (#2702)

* Fix redraw order
* Fix error when option is not defined
* Allow template labels
* Add .travis.yml file
* Add experiment travis code
* Fix react example
* Add animation to onUpdateTooltip

* fix(timeline): #778 Tooltip does not work with background items in timeline (#2703)

* Fix redraw order
* Fix error when option is not defined
* Allow template labels
* Add .travis.yml file
* Add experiment travis code
* Fix react example
* Make items z-index default to 1

* Add initial tests for Timeline PointItem (#2716)

* fix(timeline): #2679 TypeError: Cannot read property 'hasOwnProperty' of null (#2735)

* Fix redraw order
* Fix error when option is not defined
* Allow template labels
* Add .travis.yml file
* Add experiment travis code
* Fix react example
* Fix bug in item editable

* feat(timeline): #2647 Dynamic rolling mode option (#2705)

* Fix redraw order
* Fix error when option is not defined
* Allow template labels
* Add .travis.yml file
* Add experiment travis code
* Fix react example
* Add toggleRollingMode option
* Update docs with toggleRollingMode option

* fixes timestep next issue (#2732)

* feat(timeline): added new locales for french and espanol (#2723)

* Fix eslint problem on Travis. (#2744)

* fix: Range.js "event" is undeclared (#2749)

* fix(timeline): #2720 Problems with option editable (#2743)

Clean up and centralise edit status for Timeline Items.

* feat(network): Improve the performance of the network layout engine (#2729)

* Improve the performance of the network layout engine

Short-cut the execution of a number of methods in LayoutEngine to make them
handle highly-connected graphs better.

* Demonstrations of layouts of large networks

* Added support to supply an end to bar charts to have them scale (#2760)

* Added support to supply an X2 to bar charts to have them scale

* Fixed graph2d stacking issue.  It no longer takes into account hidden items

* Changed x2 to end per recommendation and added this to the docs

* Initial tests for timeline ItemSet. (#2750)

Somewhat more complicated setup, associated with the need for a real window.

* [Timeline] Modify redraw logic to treat scroll as needing restack. (#2774)

This addresses #1982 and #1417.

It possibly reduces performance, but correctness seems better.

* fix(timeline): #2672 Item events original event (#2704)

* Fix redraw order

* Fix error when option is not defined

* Allow template labels

* Add .travis.yml file

* Add experiment travis code

* Fix react example

* Fix events returned from mouse events

* Fix example

* Rename censor to stringifyObject in example

* [timeline] Update examples to use ISOString format. (#2791)

Resolves #2790

* [timeline] Update serialization example to use ISOString dates. (#2789)

Resolves #2696

* added github templates for issues and pull-requests (#2787)

fixes #2418

* feat(timeline): Add item data as argument to the template function (#2799)

* Fix regression introduced in #2743. (#2796)

* Fix for issue #2536 (#2803)

* Fix for issue #2536

* Adjusted documentation for fix.

* Adjustments due to review

* Grrrrr whitespace

* Fixed Travis issue

* Cheap fix for bug #2795

* Update to PR #2826 to use newline format

* Update to gitignore to reflect changes on remote

* clean dist folder

* Local gitignore update

* Just a first example file for the week scale feature

* Allowing sourcemap creation

* Initial (non-functional) commit to ensure we insert code at the right places (check TODOs)

* Functional, not bug-free version which works with locale aware week numbers.

* Locale-aware implementation and simplified major labels to a full year

* Trying to make the major labels show the correct start date

* Working implementation of week numbers using localization.

* removing development leftovers

* Updated package.json

* Reintagrate package.json from accidental deletion

* Updates for package.json

* Fixing package.json

* Integrate the week numbers feature in the documentation.

* Reverting local changes to .gitignore

* Reverting local changes

* Extending examples to cover the case when 1st day of week and 1st day of month align; Fixing display bug so that week numbers are not repeated in minorLabels

* Putting the examples into a loop

* Fix redraw order

* Fix error when option is not defined

* Allow template labels

* Add .travis.yml file

* Add experiment travis code

* Fix react example

* Add drop event info

* Fix redraw order

* Fix error when option is not defined

* Allow template labels

* Add .travis.yml file

* Add experiment travis code

* Fix react example

* Add callback functions to moveTo, zoomIn, zoomOut and setWindow

* styling support for graph3d tooltips

* styling support for graph3d tooltips

* graph3d styling example, deleted new example and altered the original

* graph3d tooltip styling, documentation

* graph3d tooltip styling, use the util module's method for merging objects

* Fix redraw order

* Fix error when option is not defined

* Allow template labels

* Add .travis.yml file

* Add experiment travis code

* Fix react example

* Add animation options for zoomIn and zoomOut

* Adjusted doc for autoscaling; ref Issue #2540

* Edited Defaults column for Min/Max options for completeness

This is to reduce breakage if the fallback / default changes in a future release.

* Add edited data as argument to the template function

* Update index.html

* Fix for issue #2536

* Adjusted documentation for fix.

* Adjustments due to review

* Grrrrr whitespace

* Fixed Travis issue

* Added support to supply an X2 to bar charts to have them scale

* Fixed graph2d stacking issue.  It no longer takes into account hidden items

* Changed x2 to end per recommendation and added this to the docs

* Fix redraw order
* Fix error when option is not defined
* Allow template labels
* Add .travis.yml file
* Add experiment travis code
* Fix react example
* Add toggleRollingMode option
* Update docs with toggleRollingMode option

* Added showX(YZ)Axis to Graph3d

* Added show_Axis options to docs and playground example

* Resolved merge conflict

* Added show_Axis options to docs and playground example

* change setCustomTimeTitle title parameter, Now could be an string or a function
* Fixed indent and spacing

* fix #2613 with if statement, and null for pointer value rather than referencing it when undefined

* removed if statement, since not needed, and updated documentation to note the null pointer property in certain conditions.

- Also updated docs and examples for this
 - Fixed the positioning of the tooltip if groups was enabled
 - Removed missing parameters from Popup docstring

* Fix redraw order
* Add mouseup, mousedown, mouseover, click and dblclick events on timeline
* Add docs
* Add to evenlistener example
* Add mousemove event listener
* Fix example
* Remove mouseUp and mouseDown events and fix docs for mouseOver
* Remove mouseUp and mouseDown from example

* Fix redraw order
* Fix error when option is not defined
* Allow template labels
* Fix boolean types bug
* Add subgroup stacking
* Almost finish subgroup stacking
* Play with examples for subgroup order
* Fix stacked subgroups
* Fix subgroup stacking
* Add stackSubgroups option
* Fix example
* Add docs
* Fix onRemove item subgroups recalculate
* Return subgroup example and add stackSubgroup example
* Split stackSubgroup example to subgroup/html and expectedVsActualTimesItems.html

* Added HTML tooltip support for Timeline

* Fixed tooltip position on Firefox

* Added Timeline tooltip example

* Updated tooltip location to be next to the mouse

* Added HTML element to example

* readded depricated option throttleRedraw; fixes #2511

* added doc style for depricated options

* element characteristic changes
* assume edge color inheritance is correct before choosing
* Adjust nodes’ chosen’s boolean -> bool
* Need to get user-reset size
* make example edges thicker for more noticeable shadow
* preemptive ES6 fix (see #2500/#2501)
* documentation for the feature that was previously overwritten

* Fix groupEditable
* Fix group drag in vertical direction bug
* Fix indentation
* Add initial nestedGroups property
* Fix redraw order
* Get nested groups hiding working
* Add order to nestedGroups
* Fix up example
* Add support for intially closed nested groups
* Add nested groups indentation
* Fix indents
* Add nested groups docs
* Fix example
* Revert indents
* Add classes to nested and nesting group labels and add nesting group css
* Use pure css for nested group icons
* Remove commented off lines and unnecessary btn
* Fix indents
* Add support to showNested:false in group
* Add semicolon
* Remove empty lines

* Fix redraw order

* Add initial itemVisibleFrame

* Add visibleFrameTemplate option

* Improve example

* Rename and fix example

* Fix comments from PR

* Fix example

* Add initial support for rolling mode
* Add rollingModeBtn and simplify example
* Make icon in css:
* Remove icon btn
* Add docs
* Fix zoom in rolling mode and initial start/end times

* Fix redraw order
* Add elements censor and event to emitter
* Fix all recursive loop in json event
* Add docs for event emitted

* Multifont node and edge labels
* adjust documentation
* rework mod-font property inheritance
* Node max/min widths, min heights; Edge max widths
* Accumulate sizes correctly for unconstrained multipoint labels
* handle font.multi when groupOptions.font is not declared
* propagate label fonts on changes, not just creation
* Allow top-level constraint numbers
* accumulate width and empty lines appropriately

* add pointer position to zoom event
* Update docs with zoom api

* { manipulation: { editEdge: { editWithoutDrag: function } } } edits an edge without dragging.
* An example of editing network edges without dragging, enabling label creation / change

* Added group option to change the visibility of a group
* updated the groupsEditable example page to demo the use of this feature
* updated the timeline documentation to describe this option

* Fixed bug introduced in #2284 where overrideItems is set to true when boolean is provided
* Added the option of supplying object to item.editable with updateTime, updateGroup, and remove functioning similarly to timeline.editable but only on a single item
* Updated Documentation to reflect the new feature
* Updated the individualEditableItems example page to show feature usage.

dataColor.fill and dataFill.stroke had wrong descriptions.