Refs #354: Require login on RapidSMS pages

- Added @login_required to all views that people visit
- Fixed login so it goes back to the view you were aiming for
  when you had to login
- Cleaned up some imports and PEP-8 issues
- Fixed a couple of uses of the deprecated .peer attribute
Refs #354: Mention new login requirement in release notes
Merge pull request #354 from rapidsms/354-require-login

Require login/permissions on all views