docker-compose.yml will need updating

This issue has yet to happen, but it's coming down the pipe.

Eventually Jason Wilder (@jwilder on GitHub) will be handing off his project `https://github.com/nginx-proxy/nginx-proxy` to the nginx-proxy org. As stated in [this issue](https://github.com/nginx-proxy/nginx-proxy/issues/1304) the dockerhub where we're currently pulling from will become out of date. The project we use to architect our backend has grown larger than its single maintainer, so it would be best to follow closely. There will almost certainly be upstream changes.