Refs #350: Changes as a result of testing rapidsms-appointments

    - msg.responses now contains dictionaries, not messages
    - cope with apps using old `connection` parameter for messages for now,
      but issue deprecation warning
    - allow for djappsettings not being installed
    - issue errors for some old ways of calling things that we can't handle
      anymore.
Merge remote-tracking branch 'remotes/origin/develop' into 350-test-other-apps
Merge remote-tracking branch 'remotes/origin/develop' into 350-test-other-apps

Conflicts:
	rapidsms/messages/base.py
	rapidsms/messages/incoming.py
Merge pull request #350 from rapidsms/350-test-other-apps

Try 0.13 with an existing app