Centers logo on welcome page
Adds margin to sign up inputs
Removes old bootstrap dropdown line
Updates course displays for mnemonic and number
Fixes issue with course_professor page

If a class had only reviews with no comments, then the ratings would not get calculated.
Also refactored a variable
(big-ish) Updates new review page

Updates Amount reading/writing/groupwork/hw to use new bootstrap
Updates ratings to use JQuery UI Sliders