Add some event styling.

Adds basic styling to events to imitate the styles of github.com.

![screen shot 2014-04-13 at 4 58 12 pm](https://cloud.githubusercontent.com/assets/185926/2689019/599cd2e8-c2dd-11e3-9bc1-9957abd2dfa3.png)

I haven't been particularly thorough, so I may have missed event types.

I also tried to merge master in to bring the branch up to date, but there were a bunch of conflicts, so I didn't mess with that :shit: in the interests of keeping this simple.