Grscheller.boring-math

* fixed some negative value edge cases
* lcm(0,0) now gives 0 instead of a divide by zero exception
* some authors leave lcm(0, 0) as undefined
* lcm(0, 0) = 0 does make sense
* since a*0 = 0 for all a >= 0
* 0 is the smallest non-negative integer a such that a*0 = 0
* most math theorems remain true for this case
* README.md improvements

* initial PyPI grscheller.boring-math release
* updated pyproject.toml to align with grscheller.datastructures

* working on pyproject.toml infrastructure for PyPI releases
* will use Flit as the packaging/publishing tool
* replaced bin/ scripts with `boring_math.integer_math_cli` entry-points

* first coding changes in years!
* gh-pages configured

* added pyproject.toml

* got package working again
* did not understand iterators that well when I first wrote this package
* replaced my `take` with `itertools.islice`
* generated docs from docstrings with pdoc3