List active matches in contributions tab

# Organization match
![screen shot 2014-05-23 at 12 56 28 am](https://cloud.githubusercontent.com/assets/667753/3062958/646ff4be-e22e-11e3-9eb6-c43ae906f57b.png)

# Common user match
![screen shot 2014-05-23 at 12 54 47 am](https://cloud.githubusercontent.com/assets/667753/3062957/646bf864-e22e-11e3-911d-b34da9120c0b.png)

# Without active matches
![screen shot 2014-05-23 at 1 00 36 am](https://cloud.githubusercontent.com/assets/667753/3062971/e1232c88-e22e-11e3-8d04-eabb171ea6c3.png)

Closes #233.