Update Dockerfile
While creating my own docker stack, I was looking at your dockerfile. I think it could use some work, utilize some of the newer features and reduce layer + image size.
I could work on that. Just one question to make sure no effort goes to waste:
On your DockerHub page you say, that you support docker "down to 1.12 on a best-effort basis". Do you want to keep this compatibility or can it be sacrificed (by using new docker features)?