Joeflow

* Resolve 8 -- Use a DB table lock over a Redis lock
* Fix 7 -- Switch to `varchar` from `text` to support Oracle indices

* Add Dramatiq support as an alternative to Celery
* Add Django 3.0 support
* Add Python 3.8 support

* Fix package setup (drop pbr)
* Switch to GitHub actions (drop travis-ci)
* Add Django 2.2 LTS support
* Drop older Django versions from CI
* Add isort linting
* Fix various flake8 errors
* Fix dublicate test naming

Initival code release. All future releases will follow semver.