Fix highlighting for git commits

I hope I'm not bothering you with these pull requests :)

Before:

![screen shot 2013-12-21 at 18 12 59](https://f.cloud.github.com/assets/795488/1796294/4a99dd9e-6a64-11e3-840e-52b9d5898d49.png)

After:

![screen shot 2013-12-21 at 18 13 18](https://f.cloud.github.com/assets/795488/1796292/f89cb534-6a63-11e3-9f7b-a4785ad669d3.png)