US3 Upgrade to rails 4.

Changed code that caused deprecation warnings.

Update gems to be rails 4 compat.

Went through rails 3.2.x -> 4.0 upgrade page.
US3 Move secret key base to external location in prod.

Also remove rails 3 secret token since we'll purely use the rails 4
variation.
Merge pull request #4 from winterchord/upgrade_rails_4

Update to rails 4.