Add leaderboard

### What is the problem / feature ?

There wasn't a leaderboard!

### How did it get fixed / implemented ?

I made one!  It needs to get styled cause its super ugly.

### How can someone test / see it ?

Navigate to the leaderboard link in the top nav.

*Here is a cute baby animal picture for your troubles...*

![8850200-bunnies](https://cloud.githubusercontent.com/assets/824194/2546394/7d2ba32e-b635-11e3-9b37-aa32e9d6516a.jpg)