fix(app-emulation/docker): start with a clean slate
feat(app-emulation/docker): bump to docker 0.7.1
feat(app-emulation/docker): use the coreos unit file

On CoreOS we use systemd to manage docker containers. Having docker
automatically start containers on reboot makes everything confused. Stop
doing this.
Merge pull request #275 from philips/docker-0.7.1

Docker 0.7.1