Add pytests, adjust pin bounds

[CBroz1]

I initially set out to address #241 by running the notebooks, adjusting pins, and inspecting output. Given the combinatorial issue of multiple pins, and interacting dependencies, I used some anthropic credits to turn the notebooks into a test suite.

Based on maintainer feedback, I can keep or remove any of the following...

• setup.py -> pyproject.toml
• Expanded pin bounds
• Source code notes on upper bound issues
• Source code edits to further raise upper bounds (e.g., try obj.current_func; except obj.new_func)
• Test suite
• README edits with test/coverage badges
• Github workflow
  • Weekly tests
  • On commit/PR tests