Migrate to `pyproject.toml`

[jGaboardi]

This PR resolves #200 and performs more rigorous linting, clean up, etc. Also, with added doctesting coverage goes up to 88%.

[codecov[bot]]

Codecov Report

Merging #203 (3e62357) into main (711fa81) will increase coverage by 17.2%. The diff coverage is 74.6%.

@@           Coverage Diff            @@
##            main    #203      +/-   ##
========================================
+ Coverage   70.5%   87.8%   +17.2%     
========================================
  Files         16       9       -7     
  Lines       1880    1429     -451     
  Branches     288       0     -288     
========================================
- Hits        1326    1254      -72     
+ Misses       530     175     -355     
+ Partials      24       0      -24     

Files	Coverage Δ
giddy/__init__.py	100.0% <100.0%> (ø)
giddy/components.py	93.2% <100.0%> (+79.5%)	:arrow_up:
giddy/ergodic.py	96.3% <100.0%> (+3.6%)	:arrow_up:
giddy/mobility.py	93.1% <ø> (+10.3%)	:arrow_up:
giddy/rank.py	98.4% <100.0%> (+43.7%)	:arrow_up:
giddy/sequence.py	100.0% <100.0%> (+2.6%)	:arrow_up:
giddy/util.py	100.0% <100.0%> (+2.9%)	:arrow_up:
giddy/directional.py	87.0% <50.0%> (+31.0%)	:arrow_up:
giddy/markov.py	77.4% <57.6%> (+21.7%)	:arrow_up:

... and 7 files with indirect coverage changes