Fade status when it's hovered with the mouse

fixed #1987

review: @devoncarew

![screen shot 2014-07-07 at 6 23 25 pm](https://cloud.githubusercontent.com/assets/332168/3504052/88974fd4-063e-11e4-8fb2-d44f900b510b.png)

Since the height is slightly more than the actual status bar height, I leave it in this class.