Code reformatting to black style

[jrzkaminski]

Reformatted code according to modern and convenient black style, plus added a black style badge to the README

[codecov-commenter]

Codecov Report

Merging #66 (33ad9be) into master (45c33e0) will increase coverage by 0.22%.
The diff coverage is 63.96%.

@@            Coverage Diff             @@
##           master      #66      +/-   ##
==========================================
+ Coverage   65.15%   65.38%   +0.22%     
==========================================
  Files          32       32              
  Lines        2256     2256              
==========================================
+ Hits         1470     1475       +5     
+ Misses        786      781       -5     

Impacted Files	Coverage Δ
bamt/networks/big_brave_bn.py	0.00% <0.00%> (ø)
bamt/networks/continuous_bn.py	0.00% <0.00%> (ø)
bamt/networks/discrete_bn.py	0.00% <0.00%> (ø)
bamt/nodes/__init__.py	100.00% <ø> (ø)
bamt/preprocess/graph.py	50.00% <ø> (ø)
bamt/utils/MathUtils.py	41.98% <28.57%> (ø)
bamt/mi_entropy_gauss.py	29.12% <29.03%> (ø)
bamt/redef_HC.py	56.32% <30.00%> (ø)
bamt/preprocess/discretization.py	30.30% <41.17%> (ø)
bamt/networks/base.py	48.12% <44.30%> (ø)
... and 21 more