Support mapping specific ports in "docker-compose run"

[bfirsh]

It should be possible to pass the -p option to expose ports when doing docker-compose run. It should probably be not be possible to use this option in combination with the --service-ports option.

This is part of #363.

[mrfuxi]

I started looking into this and I think I have it working. Have to write tests and docs.
Can I be assigned to this ticket, please?

[aanand]

@mrfuxi Great! I don't think non-staff can be assigned, but feel free to submit the PR in an unfinished state if you want early feedback.

[mrfuxi]

I did as you suggested, thanks @aanand