Cornerstone: The Next Generation

This PR represents the next generation of Cornerstone.

Primarily, Cornerstone is a documentation site containing best practices regarding all public facing communication about Rackspace as a company, specifically around content, visual, and brand guidelines.

In addition, it will contain source files for CSS that can be easily dropped into a new or existing website. This approach will allow Rackspace web properties to quickly and easily get on the same page from a style perspective.

Technologies used:

* Ruby (2.0)
* Bundler (1.5)
* Sass (3.3)
* Jekyll (1.4)

/cc @roycestewart @vkarnes @elblakeo