Darker background when no files

This is the same colour as the background when an empty file is open.
In hex this colour is `#272a32`.

![screen shot 2014-01-22 at 19 31 26](https://f.cloud.github.com/assets/178448/1977149/5a4c3c7a-8394-11e3-846a-e8bb914f2093.png)