Diff with better colors and some spacing on the corners

I've done some minor changes to the commit diff area, that took some inspirations by what we have here in github. With you like and merge it.

![Captura de tela de 2013-04-21 05:17:17](https://f.cloud.github.com/assets/20575/406119/4957def8-aa5d-11e2-9a3b-c0f397459eeb.png)