[Borgbackup] Borg Docker image

[Peter Schiffer]

Hello,

recently I found out about Borg and I started to really like it. I was
looking for a Docker image with Borg, but didn't find any useful enough
which would work more in a container way (configuration mostly done by
env vars), so I've created one: https://hub.docker.com/r/pschiffe/borg/

I'm writing here just to let you know, maybe it'll be useful for
somebody. If you have any feedback for the image, or if I did something
horribly wrong, please let me know :-)

peter