New nav design

 * Add `has-new-navigation` class to body when new navigation is on
 * Fix commercial Sass issues to get compilation to work again
 * Rename NewNav into NewNavigation
 * Add Guss Colours and update Guss

![screen shot 2014-06-17 at 12 15 03](https://cloud.githubusercontent.com/assets/85783/3299349/b5596b80-f610-11e3-9588-ee7620a05fa7.PNG)

![screen shot 2014-06-17 at 12 15 17](https://cloud.githubusercontent.com/assets/85783/3299351/b76d6732-f610-11e3-8686-f5e160d6108f.PNG)

![ ](http://media.giphy.com/media/HCE5XnvKf17Lq/giphy.gif)