Clean-up Galois field array code and tests

[mhostetter]

No description provided.

[codecov]

Codecov Report

Merging #173 (722c4dc) into master (1a459a7) will increase coverage by 0.80%.
The diff coverage is 87.32%.

@@            Coverage Diff             @@
##           master     #173      +/-   ##
==========================================
+ Coverage   91.65%   92.46%   +0.80%     
==========================================
  Files          37       37              
  Lines        4304     4235      -69     
==========================================
- Hits         3945     3916      -29     
+ Misses        359      319      -40     

Impacted Files	Coverage Δ
galois/_fields/_array.py	89.15% <ø> (+0.66%)	⬆️
galois/_fields/_class.py	90.00% <ø> (+1.44%)	⬆️
galois/_lfsr.py	93.16% <66.66%> (ø)
galois/_fields/_functions.py	82.23% <74.41%> (-8.59%)	⬇️
galois/_fields/_lookup.py	91.13% <84.09%> (+6.61%)	⬆️
galois/_fields/_gfp.py	90.81% <89.23%> (-7.06%)	⬇️
galois/_fields/_gf2m.py	91.34% <90.00%> (-5.66%)	⬇️
galois/_fields/_gfpm.py	94.94% <94.11%> (-3.04%)	⬇️
galois/_codes/_bch.py	97.98% <100.00%> (+0.48%)	⬆️
galois/_codes/_reed_solomon.py	98.69% <100.00%> (+0.64%)	⬆️
... and 11 more

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