Renamed transactions#extend to extend_expiration.

RSpec was whining about having controller actions named extend and it didn't
work out very well. Decided to just rename it something else.
Adding permission tests for administration pages.
Updating TODO.
Fixing bugged translations.
Remove order of association.
Order lists in event admin interface appropriately.
Major cleanup in authorization code.
Adding small explanation in comment.
Remove redirect loop when insufficient access.
Updating README.