Added a default implementation for the username block when offline

This way the username block appears the correct color:

![screen shot 2014-05-14 at 03 30 19](https://cloud.githubusercontent.com/assets/1578238/2968016/b6bdcd5a-db39-11e3-9b42-820e81c1c40d.png)

instead of the "unimplemented" color:

![screen shot 2014-05-14 at 03 30 50](https://cloud.githubusercontent.com/assets/1578238/2968017/bb1fef22-db39-11e3-9e5e-ae68395f2a0f.png)