Reworked login UI/UX

++ WBErrorNoticeView for a smoother user experience (got rid of that
ugly label).  As a consequence of that, dismissing the keyboard is no
longer necessary.
++ReactiveCocoa
Removed color update in favor of draw block
Removed operations; Made classes RACAble
Made fetching repositories first priority
Added KRGithubRepository wrapper class
Added account manager and reachability
++WBNoticeView