Sass refactoring

Cleaning up a lot of the CSS code and in the process, re-doing the header section on the landing page.
![screen shot 2014-10-24 at 6 09 35 pm](https://cloud.githubusercontent.com/assets/1807325/4778271/9c3aacf2-5be3-11e4-8dde-bc0fa4c870a8.png)