* 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>