Add bumpversion for easier version bumping

[mpacer]

bumpversion is a python library that allows you to automatically change the version number of a package in all the places that it needs to be changed using a simple CLI.

This would make updating version numbers for releases substantially easier.

General steps:

• [ ] add bumpversion as dependency
• [ ] Identify all places in code where version bumps would be needed see here
• [ ] confirm version number practices (e.g., does it involve beta releases, *dev releases?)
• [ ] write bumpversion.cfg to match this behaviour.
• [ ] update docs to explain how to use bumpversion