add docker-compose + Dockerfile support

[alee]

Provides proof-of-concept docker support for #558

• could also add a shell script or Makefile to make it easier to invoke
• does the Docker documentation belong in this top level readme.rst or the CONTRIBUTING.rst?

[coveralls]

Coverage remained the same at 79.773% when pulling e526875 on comses:dockerfile into 70cc59d on projectmesa:master.

[jackiekazil]

After doing a review of this, this all looks good. Thank you for this confirmation. I few people were asking for something like this, and I think it will be helpful!