Add separate icon for .scss & .sass files

[Dix Huit]

First up - thanks for this theme. It was instrumental in me returning to Sublime Text after a while :)

I'd love to see some distinction between CSS files and Sass source files (.scss/.sass) in terms of sidebar icons - currently they all appear to use the CSS3-style icon.

[Max Riveiro]

@danbohea Could you pass me icons for SASS and SCSS? I tried to find them, but failed :(
P.S. LESS icon also will be appreciated ;)