Adds `gunicorn.conf` entrypoint and `FlaskLauncher` CLI template.
* Merges 23
* Fixes 20
* PEP updates to internal logging calls, `%` formatting
* Improves code smells per [CodeClimate report](https://codeclimate.com/github/EVEprosper/ProsperCommon/pull/23)
* Prunes deprecated code from `prosper_config`
* Removes `prosper_utils`. Moving to [ProsperTestUtils](https://github.com/EVEprosper/ProsperTestUtils)
* Improves test coverage for `prosper_cli`
* Increments docs for new features
* PEP: adding trailing commas