Add tests based on python's itertools

[natemcintosh]

Feel free to ignore and close this PR without explanation.

The basic idea here is to test the Julia version against the python itertools.

Assumptions: python's itertools library is correct.

• Benefits:
  • Can verify behavior for longer sequences. This could help find corner cases not explored in the current, smaller test set.
  • Greatly expands the test set with only a little code added to the repo.
• Downsides:
  • If the algorithms are ever changed in such a way that the order of combinations/permutations produced changes, these tests will be useless, and will have to be removed.
  • Have to add PyCall as a test dependency. Could make CI take longer to run.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 96.97%. Comparing base (8a7a8ac) to head (a597eb0).
Report is 37 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master     #130   +/-   ##
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  Coverage   96.97%   96.97%           
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  Files           7        7           
  Lines         728      728           
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  Hits          706      706           
  Misses         22       22           

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[natemcintosh]

Looks like the failure on Julia 1.0 on windows is because PyCall failed to build. Not sure how to get around that