* Add template for document generation with 'jsdoc'.

In essence, it defines the subdirectory `docs` as a `jsdoc` template. Benefits:

- allows the usage of partials, in order to DRY common parts of the html files.
- makes available the jsdoc-comments, for addition into the documentation.
- enables extraction of data from the source code. For example, the list of edge endpoints `['arrow', 'bar', 'circle']` can now be extracted from the source and inserted into the documentation on generation.

In this initial version, the only file that has been changed is `docs/data/dataset.html`.
In here, partials have been added to illustrate how common page elements can be DRY'd.

The template has been set up in such a way, that resource files will be copied and that html files can pass through unchanged if no special template tags (`<?js...?>`) are used. This allows for a gradual transition of the html files to templates.

**Usage:**  `gulp docs`

- The result files are placed in subdirectory `gen/docs/`.

**NOTE:** The release procedure will have to be adjusted by adding this gulp command.
The docs-files will then have to be taken from `gen/docs`.

* Edits to docs/README

* Adjusted layout of README.md

* Further edits to README.md

* Removed pre tags again in  README.md - don't work in code block

* Linted the gulpfile

* Added proof of concept for docs generation from source

* Enable linting for Travis

Since all code has been linted (thanks **TODO**!), it is now safe to enable linting for Travis.

Some cleanup actions have been performed; notably the additional `gulp` tasks for modules has
been removed. Since all code has been fixed for linting, these are not useful any more.

* Force linting error to check travis working

* Travis works! Remove forced linting error

* First working version of eslint enabled with gulp

* Tryout of eslint with graph3d files

* Cleanup of gulp and eslint files.

* Completed test by linting graph3d

* Disable travis linting for now

* Remove global cmd param from .travis.yml

* Add C++11 and canvas module for travis tests

* Added libgif, updated version gulp-clean-css

* Update version webpack

* Force versions minimatch, graceful-fs; fixes for upgraded webpack

* Force version minimatch through travis.yml

* Fix comma's in json

* Add extraneous modules to package.json; final attempt at forcing versions of minimatch and graceful-fs

* Final changes module versions

* Fix due to linting

* Fix typo in package.json

* Upgrade eslint

* move all babel options to .babelrc file

* updated babel-loader

Fixes: https://github.com/almende/vis/issues/2490

* generate individual css files; fixes #1969
* simplified css bundleing
* add new generated dist-css files
* use chart specific css files in the examples

* replaced deprecated gulp-minify-css with gulp-clean-css
* updated mocha

`vis-network.min.js`, and `vis-timeline-graph2d.min.js`

Signed-off-by: Marlos Dantas <dantas_marlos@apple.com>