Hide status bar for medium screens

It closes #367.

It looks like this: 
![screen shot 2014-06-11 at 2 18 43 pm](https://cloud.githubusercontent.com/assets/230476/3244718/1a3d3996-f16b-11e3-9b39-e11f45679ad3.png)

The `.hide-for-medium` would not hide the element in small screens?