Add windows build tool appveyor

[agrandville]

for now, no change to source code or cmake script.
Build fails, fixes to follow.

[benmcollins]

Is there anyway you can use Travis-CI instead? I already use that, and I hesitate to add another CI setup in the code.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 87.51%. Comparing base (1476ec1) to head (079f4f8).
Report is 8 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master     #191   +/-   ##
=======================================
  Coverage   87.51%   87.51%           
=======================================
  Files           3        3           
  Lines        1145     1145           
=======================================
  Hits         1002     1002           
  Misses        143      143           

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