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
Arbitrarily long sleeps should be avoided where possible, since timing can vary widely between machines, and you both want to support slow machines while responding more quickly on a fast machine. Better here would be to put in a loop that verifies that RabbitMQ is up somehow (with a maximum timeout to avoid waiting forever and a relatively high frequency to respond quickly on fast machines).