Add some more typing

[devdanzin]

This PR adds some more typing information, including handling most complaints from mypy.

[codecov-commenter]

Codecov Report

Patch coverage: 95.91% and project coverage change: +0.03% 🎉

Comparison is base (099bc78) 95.84% compared to head (e4b59ff) 95.88%.

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #221      +/-   ##
==========================================
+ Coverage   95.84%   95.88%   +0.03%     
==========================================
  Files          25       25              
  Lines        1349     1362      +13     
  Branches      289      289              
==========================================
+ Hits         1293     1306      +13     
  Misses         32       32              
  Partials       24       24              

Files Changed	Coverage Δ
src/wily/archivers/git.py	87.65% <60.00%> (ø)
src/wily/archivers/__init__.py	94.23% <100.00%> (+0.11%)	⬆️
src/wily/commands/build.py	92.78% <100.00%> (ø)
src/wily/commands/graph.py	100.00% <100.00%> (ø)
src/wily/commands/index.py	100.00% <100.00%> (ø)
src/wily/commands/rank.py	96.61% <100.00%> (ø)
src/wily/commands/report.py	97.24% <100.00%> (-0.03%)	⬇️
src/wily/config/__init__.py	100.00% <100.00%> (ø)
src/wily/helper/__init__.py	100.00% <100.00%> (ø)
src/wily/operators/__init__.py	97.82% <100.00%> (+0.02%)	⬆️
... and 4 more

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