Develop header colour

Adds a bold header section across top level pages on the site.
A theme to explore on #show pages and others now.

![screen shot 2014-10-01 at 5 47 19 pm](https://cloud.githubusercontent.com/assets/1239550/4470438/26342a8a-4926-11e4-94ba-4019ab3e1fc1.png)

closes #600