Add support for FontAwesome icons

I take no credit for `fontawesome.sty` myself, I just found it in a gist by Honza Ustohal and thought it was a nice touch to my personal fork. `fontawesome-webfont.ttf`, added to the `fonts` directory, must be installed as an OSX system font, after which this works rather seamlessly.

Example use:
`\href{http://twitter.com/swaycz}{\twitter\ swaycz}`

A number of definitions are included already in `fontawesome.sty`, but arbitrary new definitions can be included as well.