I've added optional ssh tunnel functionality based on the tunnel-ssh package (https://github.com/agebrock/tunnel-ssh#readme). I've been using a fork of this repo internally at my company for some time to run migrations on our production databases, however we're using AWS DocumentDB which cannot be connected to without the use of an ssh tunnel. Just thought I'd contribute back to the project as I suspect some others may find use in this feature too.

I'm not entirely sure the approach I should take in testing this feature. I figured I'd get some feedback on the PR first before taking the time to figure out the testing. Let me know if this is a feature you'd like to add, and any suggestions you may have with respect to testing.

Checklist

• npm test passes and has 100% coverage
• [ x] README.md is updated