feat(docker registry): add Vagrantfile for Docker registry

Adds a contrib/docker-registry directory with a Vagrantfile that
configures and starts a VM with the Docker registry service.
fix(docker-registry): up timeout

Slow connections wouldn't pull the image in under 90 seconds.
Merge pull request #1135 from deis/feat-local_registry

feat(docker registry): add Vagrantfile for Docker registry