Remove redundant operator definitions

[christiangnrd]

!= should be covered by the == definition above, and the other equality operators all fall back to <, so only define < (and <= for 1.6 and 1.7).

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 72.77%. Comparing base (f762420) to head (0f527db).
Report is 9 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master      #93      +/-   ##
==========================================
+ Coverage   72.10%   72.77%   +0.66%     
==========================================
  Files           3        3              
  Lines         190      191       +1     
==========================================
+ Hits          137      139       +2     
+ Misses         53       52       -1     

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[christiangnrd]

Thank you @oscardssmith for taking the time to for review and merge! Can we tag a release? No bump needed since the repo was bumped to 0.5.1 back in september and never registered. It would also close #90.

[oscardssmith]

will do!