Use docker

Docker support for development.

* added Dockerfile to support the creation of Docker containers
* updated README with information on how to setup a Docker container
Given that running the tests is dangerous, since it can wipe out data, I actually think we should default to True here, and ideally detect if we can run docker at the beginning of the tests, erroring out if we can't, with a suggestion on how to run against an existing (test) installation of RabbitMQ.