Current tasks (0.9.0)

The issues release, a.k.a. issues, issues everywhere!

• [x] Check the circle-ci setup.
• [x] Migrate from pipenv to poetry.
• [x] Start using black.
• [x] Cleanup of coverall/codecov properties.
• [x] Document using docstrings and Sphinx.
• [x] Start using github issues.
• [ ] Clear all the issues with a ‘test’ label. 6 to go.
• [x] Document the architecture.
• [ ] Explain the ci/development flow.