Base snappy bouncer

Flow of communications:

- [x] Ticket logged by POST to `/snappyconfirm/ticket/` endpoint 
- [x] `post_save` signal triggers Celery task to pipe to Snappy
- [x] User selects FAQ response on Snappy web app
- [x] `outbound.message` webhook fired by Snappy
- [x] `/snappyconfirm/listener` accepts webhook updates ticket log and triggers Celery task to send via Vumi HTTP