[WIP, ENH] Better plotting

[rmarkello]

Fixes bugs in plotting and adds new plotting features.

[codecov-io]

Codecov Report

Merging #40 into master will decrease coverage by 7.63%.
The diff coverage is 5.33%.

@@            Coverage Diff            @@
##           master     #40      +/-   ##
=========================================
- Coverage   96.03%   88.4%   -7.64%     
=========================================
  Files          21      23       +2     
  Lines         882     888       +6     
=========================================
- Hits          847     785      -62     
- Misses         35     103      +68

Impacted Files	Coverage Δ
pyls/plotting/__init__.py	0% <0%> (ø)
pyls/plotting/meancentered.py	0% <0%> (ø)
pyls/plotting/behavioral.py	0% <0%> (ø)
pyls/plotting/utils.py	0% <0%> (ø)
pyls/types/meancentered.py	100% <100%> (ø)	⬆️
pyls/types/behavioral.py	100% <100%> (ø)	⬆️
pyls/base.py	94.59% <0%> (-0.33%)	⬇️
pyls/structures.py	100% <0%> (ø)	⬆️
pyls/tests/__init__.py
... and 5 more

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