[Feature Request] New version detection

[rexwangcc]

As a user, I'd like to get notified from the command line if there are new versions of cromwell-tools available, so I can update.

[rexwangcc]

A good example of this would be the pip: https://github.com/pypa/pip/blob/master/src/pip/_internal/utils/outdated.py

[dinvlad]

There's also an example in Google Cloud SDK