Add stable Windows testing framework

[glenjarvis]

Feature Request

There is an appveyor.yml file in the repository that is not currently being used because of the 'flakiness' that was encountered with AppVeyor. We want to ensure Windows compliance but not having the testing framework block work unnecessarily.

We need a stable windows testing framework, even if we need to build one ourselves. However, less work would be needed if we found an outside vendor that would effectively run tests for us.

See also: https://www.appveyor.com/docs/build-environment/#python