Move docker-compose to extras

[shoelsch]

For me, docker-compose is a heavyweight dependency and my understanding is it's only used for local mode (please correct me if I'm wrong).

My particular painpoint is that taking on a docker-compose dependency means that I'm forced to downgrade PyYAML from 5.1 to <4.3. I have concerns using a PyYAML version other than 5.1 based on the vulnerability laid out here: https://github.com/yaml/pyyaml/wiki/PyYAML-yaml.load(input)-Deprecation.

I don't rely on local mode, but use Sagemaker SDK to submit remote jobs with already built Docker images. How about moving docker-compose to an extras_require for users to specify whether they want this dependency?