Add ability to pull container exit logs

[andimiller]

This adds a new method on DockerClient called getExitLogs which
returns an F[List[ExitedContainer]], you should only evaluate this F
after your Resource has completed, since this is only populated on
container cleanup.

[nicktelford]

Is it possible to not pull all the logs as a single String and perhaps use something a little more lazy? What does the Spotify client expose?

[andimiller]

The spotify client exposes an Iterator<LogMessage> by default, but I need to consume the whole iterator before I delete the docker container, which is what I do to generate the String stored in the ExitedContainer. I could add some kind of callback you can register when you make the DockerImage which would hook this up in realtime, I'm not sure which method is more fiddly to use.

[nicktelford]

I think a callback might be nicer? Might also be possible to provide a Stream[F, String] and use onFinalize to cleanup the container? The issue with this is that you'd need some way to ensure the Stream terminates.