Automated Docker build

[mehlon]

Docker allows automated builds for free for git repositories. I currently have a repository at https://github.com/mehlon/purgatorio/ which autobuilds to https://hub.docker.com/r/mehlon/purgatorio. But my repo is not automatically synced to upstream, so the Docker build is not always up to date. Something like a "9front" or "9mirrors" docker group account could be used to automate this 9mirrors repository.