chore(build): Adding Sass to Grunt pipeline

Adding Sass and Autoprefixer into the mix. This also means we need a dist/ directory, so things are about to get "weird".

Took a rough stab at documenting the available Grunt tasks, although some are subject to change once we get minification and other things involved.
The scripts will get concatenated (including the `bower_components` scripts) with r.js so that will simplify things. If we include the necessary css/sass with sass imports then sass will take care of grabbing those from `bower_components` as well. Soo we won't have to copy `bower_components` at all pretty soon!