Stabilize code and release new version in accordance with paper release and the end of the course

[msricher]

Todo

• Clean up the contributed code from the course. I've just been doing black -l 100 on my own Python files so far, but I will add some proper pre-commit hooks to take care of this once the course is done.
• Improve C++ code comments.
• Bump version number to 0.7.0.
• Include in the README and website a section like the following with a bibtex entry once the paper is published:
  Citing PyCI:
  -----------------
  Please cite PyCI in accordance with the following if you use it for published research:

  @article{2024pyci
  ...
  }

I would also appreciate others' thoughts on what should be done during this time.