Integrate Devise auth into Dashboard

Had to redo devise auth. Not sure what went wrong on my first attempt
earlier, but this now works.

Added bootstrap elements to registration and login pages. Added a
warning bar when you either log in or out.

Problem discovered with TBS 3.0:

If you try to use the example log in page that TBS provides, Devise will
not work. That's because the second html element that they had was a
form tag. This form overwrote Devise's form, and it broke auth. Changing
it to a div tag fixed this problem and kept the css elements. Woo!

#5