Add property-based test with Hypothesmith

[Zac-HD]

Hey @timothycrosley! I saw Zac-HD/hypothesmith#8 and thought I'd write you a pull request 😄

Notable features:

• custom strategy for Config objects to explore more weird edge cases
• custom composition of Hypothesmith strategies to boost number of import statements
• custom targeting logic to boost code complexity and number of import statements

Bugs that this can find (albeit with lowish probability):

• "import A\nimportA\r\n\n", importA incorrectly treated as an import, unstable whitespace

Once you get it passing, I'd suggest using while pytest -n=auto --dist=each tests/test_hypothesmith.py ; do : ; done to soak up some CPU time looking for bugs overnight - if that doesn't find anything, it's unlikely that there's anything the test can find at all.

[codecov-commenter]

Codecov Report

Merging #1361 into develop will not change coverage.
The diff coverage is n/a.

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##           develop     #1361   +/-   ##
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  Coverage   100.00%   100.00%           
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  Files           34        34           
  Lines         2328      2328           
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  Hits          2328      2328           

[timothycrosley]

This is awesome! Thank you!