Overhaul the docs

This is a major redesign and overhaul of the docs and can be previewed at [http://ascott1.github.io/capital-framework/](http://ascott1.github.io/capital-framework/). This is by no means finished, but I think it's in a state that we can make it "official."


![selfie-0](http://i.imgur.com/NWVVClN.gif)

Hot tip for next time: http://cfpb.github.io/cf-core/docs/#media-query-mixins