Remove TWBS ads from docs pages
Looks like these files require compass to compile

I like the idea of removing the Compass dependency and depending on sass
+ autoprefixer to build the demo files, but these scss files use too
many Compass mixins to safely remove Compass as a dependency.

Fixed Compass and jekyll versions in a Gemfile.

I think I can remove autoprefixer since the Compass functions handle
most of the prefixing.