find settings for Python lint tools compatible with source code examples

[gvwilson]

1. Most of the Python files in ./src/*/*.py fail to pass flake8, isort, and black checks (run make style in the root directory to see).
2. Most of these formatting "errors" are deliberate to make code denser or to enable slicing for presentation.
3. Modify the settings in ./Makefile and/or ./setup.cfg to accept the code as-is without breaking checks for ./lib/mccole/bin/*.py and ./lib/mccole/extensions/*.py (the tools used to build the book, which aren't included in the book and so can be formatted normally).