Maintainence fixes abound; updates to support python>=3.11

[peytondmurray]

This PR introduces a number of maintenance fixes, and closes #8.

Changes

• Reorganized the package to a "src-layout", matching the setuptools documentation.
• Updated the required python version to >=3.11
• Added a a couple of much-needed pre-commit hooks, and addressed minor issues flagged by them
• Removed bump2version; I'm going to rely on setuptools_scm from now on
• Removed CircleCI configuration. I'll swap to github workflows in a subsequent PR to run CI
• Removed setup.py in favor of package configuration in pyproject.toml.
• Made package imports a little more user friendly
• Fix the notebook example to remove unused imports; clear notebook output
• Added a permissive (MIT) license
• Removed flake8 config; moved all lint configuration into pyproject.toml