Feature: header design

This adds a pleasant new design for the header, what with the angles and the psuedo-elements.

Screenshot:

![screen shot 2014-03-06 at 12 28 14 pm](https://f.cloud.github.com/assets/808159/2350233/e945e3c2-a56d-11e3-8121-088e0ea41310.png)

/cc @cherimarie @eastridge