Header fixes. Hover tooltip on Mod/Admin w/ title attribute (Implements #259)

No scrollbar on main nav (unhides logout button).
Comment out unimplemented messages area.
Add icons to nav when in mobile (xs) (doesn't play nice on lg).
Use fa-file-excel-o to represent libs (an X instead of </>).

![](http://i.imgur.com/GnKCbAH.png)
![](http://i.imgur.com/TwIBPEg.png)