Using smartmenus restores submenus on small screens

As one solution to #6759, this uses [smartmenus](https://github.com/vadikom/smartmenus) with its [bootstrap plugin](http://vadikom.github.io/smartmenus/src/demo/bootstrap-navbar.html) to make sure the menus work across devices.

iPhone example:
![2014-11-09_2123](https://cloud.githubusercontent.com/assets/45380/4970405/9e597faa-6880-11e4-8346-ad55ecd3e7d2.png)

Notes
- There are a few "extras" enabled by default, such as the caret and the show/hide effect, which can likely be turned off 
- This PR does not include the `components` upgrade, but smartmenus is listed on bower, etc.