LGTM

Please excuse me while I clean up my drool for the awesome that is this. I will definitely be reviewing this the moment I get back from lunch.

I don't like the .dck it's not a good practice, I think we should keep 2 directories with Dockerfile inside

So many kudos here (and I definitely agree with @vieux, so thanks for changing that 👍).

As one final tweak, I'd recommend you switch from tianon/debian to from tianon/debian:wheezy so that when jessie becomes stable (and thus our "latest" tag), we don't have odd behavior with your hard replacement of "/etc/apt/sources.list" to add contrib (which might even be worth switching to something like we've got in the docker-registry to add the universe: https://github.com/dotcloud/docker-registry/blob/master/Dockerfile#L3 - the benefits being that you then get to keep "-updates" and "security" repos, and upgrading the image to "jessie" at some point becomes extremely trivial).

Awesome. Thank you for reviewing this @creack, @vieux & @tianon!

Happiness!