Initial changes to add a nav element to the structure
Add basic mobile styling to the simple theme
Fix importing and demo

As it turns out, in LESS 1.3.x, you can't just randomly mix @imports
into the middle of your style rules. Until I have a LESS 1.4-compatible
compiler, we need to keep doing things the way we always have.

Unrelated, the demo was pretty broken, but that's fixed now.
Remove unnecessary nesting in menu.less
Updating branch and fixing merge conflicts
Update structure of the tan theme
Merge nav structure changes from master
Update blue and simple themes

Make the two usf-specific themes compatible with the new nav structure.