Add code-review process

[ross-spencer]

• A conversation.
• Trying to capture slightly different happy-paths and exception-paths.
• Find a common understanding.
• About progress, not perfection.
• A way to share experiences that are embedded in code to improvie it.
• Ultimately, should be safe, and rewarding.

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• Rely as much on tooling as possible:
  • black - code formatting.
  • pylint - improving style and adherence to standards.
  • flake - identify code errors and adherence to PEP guidelines and principles.
  • isort - organize imports automatically for us (and helps to ensure they function correctly).
• Future tooling to keep an eye on:
  • mypy - incoming.
  • markdwn linting - still to find.
  • docstring linting - not as important with mypy.
• Tests
  • Unit tests,
  • Behavioral driven,
  • Type-testing.