Set up project metadata

[Technologicat]

• AUTHORS.md Done in c1086e5.
  • Include also indirect contributions (e.g. Alex Leone's astpp, and the design of the quasiquote system from macropy).
  • Note which license each contribution is used under.
• CHANGELOG.md Added in 284a7bf. Now just to keep it up to date...
  • Describe changes between mcpy 2.0.0 and mcpyrate 3.0.0.
• CONTRIBUTING.md? Done in 6d1a624.
  • Could move the Understanding the code section here.
  • Follow PEP8, but not into foolish consistency.
  • A blank line (or a double-blank line when appropriate) is a paragraph break, to separate logical units. Just like when writing prose, don't break the paragraph inside a logical unit, no matter what flake8 tells you. This helps make the overall structure explicit and easy to see at a glance.
• Configure badges in README.md (see unpythonic).
  • Many badges require having the project on PyPI. For that, we first need some more automated tests, see Improve test coverage #2. Some badges require having CI, see Set up a CI workflow for coverage measurement #5.
  • Get the badge format from unpythonic's README.
• We use semver, note it somewhere? Done in 48d7fa3.
  • 6d1a624 notes it in CONTRIBUTING.md, but should add a note to README.md, too, for users.

[Technologicat]

As of 50e0e68, we're only missing CI status and codecov, which depend on #2 and #5.

[Technologicat]

As of f8d8072, we're only missing codecov.

[Technologicat]

As of f4cbb24, we have codecov, too.