Wiki: Increase font size and free space to make it more readable

This bugged me for a while. It's not perfect now, but I like it much better. Feedback welcome :)

![op-wiki-space](https://cloud.githubusercontent.com/assets/188986/3131419/506ed094-e804-11e3-9c80-7270ce645803.gif)

The one with the larger font and more free space is the new version.