MUMUP-1292: Fix search on mobile

When you hit submit the search on mobile, the search box in the header now hides, as one would expect it to.
I merged the header and search controllers into one, since the header controller wasn't really doing anything other than storing whether to show the mobile search div.

![screen recording 2014-11-12 at 11 41 am 1](https://cloud.githubusercontent.com/assets/1919535/5015215/65725878-6a61-11e4-89ba-16910d81a1bc.gif)