Add containerLogs API endpoint

[clue]

Depends on #4 (uses raw streams?)

[clue]

After investigating this further it turns out this behaves very similar to the containerAtach API endpoint (#13) and uses the same framing protocol if TTY mode is not enabled.

I'll look into this.

[clue]

Looks like many API clients resort to using the inspection API to check whether TTY mode is enabled for the given container.

https://github.com/docker/docker-py/pull/669/files
https://github.com/docker/docker/blob/master/api/client/logs.go

[clue]

• TTY disabled (default) - multiplexed stream, uses application/octet-stream content-type
• TTY enabled - raw plaintext stream, uses text/plain content-type

[clue]

Turns out this works very similar to #13:
http://stackoverflow.com/questions/26149594/what-is-the-difference-between-docker-logs-and-docker-attach