Evaluations refactoring and non-thresholded bugfix, plus test to ensu…

[thcrock]

…re that bug is fixed

[codecov-io]

Codecov Report

Merging #30 into master will increase coverage by 0.1%.
The diff coverage is 100%.

@@            Coverage Diff            @@
##           master      #30     +/-   ##
=========================================
+ Coverage   90.79%   90.89%   +0.1%     
=========================================
  Files          13       13             
  Lines         793      802      +9     
=========================================
+ Hits          720      729      +9     
  Misses         73       73

Impacted Files	Coverage Δ
catwalk/evaluation.py	96.8% <100%> (+0.33%)	⬆️

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