Add Octicons

Closes #24

Add [GitHub Octicons](http://octicons.github.com/) to GlyphSearch.

Created a quick crawler that creates the JSON file for GlyphSearch from the Octicons website, so should be easy to keep the data up-to-date. [octicons-glyphsearch-crawler](https://github.com/matiassingers/octicons-glyphsearch-crawler)

Sorry to @repat if he was already working on this.