finishing up elemental mobile nav, #364

This also includes styling for the search bar. Some notes on this one:
1.) Using view.js to append the mobile nav overlay to body tag. Since this is outside .ccm-page wrapper, had to place navigation.less import outside of the .ccm-page namespace. This approach is more theme agnostic (custom template can't really reference a class specific to the elemental theme). Within navigation.less, the mobile menu bars button is within .ccm-page namespacing, though. 

2.) Added some classes (col-sx-6) to the header divs for when they hit extra small town so that they stack side by side. Had to change the tertiary div that usually contains search to a col-sx-12, which makes it wrap under nicely, but it is a little snug against the site title div and the navigation button div. We could address that with a class on the tertiary div to give it some top margin in mobile town, or maybe there's some Bootstrap voodoo about mobile column stack spacing that I'm overlooking? 
![spacin](https://cloud.githubusercontent.com/assets/1302433/3517527/0ce12bb4-06f0-11e4-8839-d9a1a08e80db.jpg)