Redesign and CNAME

Updates design to match new [Artoo](http://artoo.io) design. Also adds CNAME file so that `gitnesse.com` will be used as the domain instead of redirecting to `hybridgroup.github.io/gitnesse`.

New look:
![New Appearance](https://f.cloud.github.com/assets/489142/1186887/abe1f276-232e-11e3-8ba3-9dac6654ca38.png)