#60 Image files in staging

![screen shot 2013-10-21 at 22 33 31](https://f.cloud.github.com/assets/5281068/1378455/ce6a759e-3aca-11e3-8c71-ff4bffe3c552.png)


Ungit now displays images in staging. Issue https://github.com/FredrikNoren/ungit/issues/60

Tested with JPG, GIF, PNG and BMP.