* Translate setup.py to pyproject.toml
* Introduce PEP518 by using Poetry as package manager
* Introduce PEP402-ish package structure
* Remove requirements.txt and setup.py
* Update Dockerfile and Docs for new packaging method
* Bump dependencies, remove six
six is no longer necessary as of docker-py 5.0.1 (see https://github.com/docker/docker-py/pull/2863)
