Nav space and overflow-prevention

Currently, items in the nav are clipped on desktop, and on the Aus nav sometimes even poke through after the toggle:

![screen shot 2014-11-20 at 16 14 09](https://cloud.githubusercontent.com/assets/867233/5128001/f244ebe8-70cf-11e4-8b4e-be999b6c2fe6.png)

This gives items in the nav more room, by restricting the toggle to “all” between desktop and leftcol breakpoints, and prevents items from poking out past the toggle in the event that they don't fit in future.