Add a "latest" tag to the docker images

[mpathy]

It's standard to add a latest tag to the docker images, which points to the, well, latest version created.
Please add it, as it is assumed not only by users, but also tools.
Kitematic on OS X already stopped at the creation because of that.

[JedMeister]

Hi @mpathy - thanks for the suggestion and it's a sound one... Unfortunately though, this project is currently somewhat in a state of hibernation. So any updates anytime soon are unlikely sorry.

Hopefully we'll get back to it soon(ish) but no promises...