Request for review: mongodb_replica_set

Hello everyone!

I’ve just submitted a pull request for the new module - mongodb_replica_set:
https://github.com/ansible/ansible/pull/5615

As the name implies, this module can be used to manage MongoDB replica sets.

Python is not my native language :), so I’d like to ask anyone available/interested to review it.
I made sure ‘make pep8’ doesn’t bark on it, but I don’t know what else to check.
Any feedback is much appreciated.

Thanks,
George