Stylus language support in Atom (with extra snippets)

Adds syntax highlighting and snippets to Stylus files in Atom.

Originally converted from the Stylus TextMate bundle and Stylus Plus bundle.

Massive hat-tip to https://github.com/billymoon/Stylus for a lot of the regex values.

Contributions are greatly appreciated. Please fork this repository and open a pull request to add snippets, make grammar tweaks, etc.