Styled "Mail" dropdown
Added app dropdown content
Added content to user dropdown
Styled checkboxes

* Requires some javascript to allow de/checking of the checkbox in
  the inbox button group (in test.coffee, which I should maybe rename)
Implemented select-all checkbox function
Implemented select all/none in inbox btn dropdown
Implemented select read/unread in dropdown
Implemented star/unstar functionality
Implemented select starred/unstarred in dropdown