Site bar redesign

Here's a simple restyling of the site bar. The bright blue and orange were quite distracting, and often clashed with the site design on the front end. I've changed to a more restrained dark design, and used the pinstripe background to maintain visual consistency with the back end.

![screen shot 2014-05-16 at 11 45 59 am](https://cloud.githubusercontent.com/assets/342659/2992165/2701d898-dc8b-11e3-8f68-8648472845c7.png)

Any thoughts?
I wonder if we can improve this: https://developers.google.com/speed/docs/best-practices/rendering#UseEfficientCSSSelectors