Move sponsors to a table layout

The current sponsor layout looks broken because lists are terrible at tabular layout unless we have fixed heights:

![screen shot 2013-09-30 at 14 07 13](https://f.cloud.github.com/assets/60786/1237185/5c210b90-29d3-11e3-90ce-53b3e25d6e8b.png)

This PR makes this tabular data a table.

![screen shot 2013-09-30 at 14 26 02](https://f.cloud.github.com/assets/60786/1237221/e1fffa46-29d3-11e3-9196-1586a6ed00f9.png)