case insensitive bug fix

[dmarkham]

fixes a bug reported by @mvrhov

[codecov-commenter]

Codecov Report

Merging #38 into master will decrease coverage by 0.14%.
The diff coverage is 0.00%.

@@            Coverage Diff             @@
##           master      #38      +/-   ##
==========================================
- Coverage   66.15%   66.00%   -0.15%     
==========================================
  Files           3        3              
  Lines         452      453       +1     
==========================================
  Hits          299      299              
- Misses        142      143       +1     
  Partials       11       11              

Impacted Files	Coverage Δ
enumer.go	100.00% <ø> (ø)
stringer.go	61.11% <0.00%> (-0.16%)	⬇️

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