A follow on PR from #561
Included a appveyor.yaml that uses tox to run tests on Windows. Tests currently pass/fail for the following reasons:
- Python 2.6: Fail - pip is not installed on Windows for Python 2.6
- Python 2.7: Passing
- Python 3.3: Fail - Needs Python 3.4 or greater to run the latest version of dependencies listed in tox.ini
- Python 3.4: Passing
- Python 3.5: Passing
- Python 3.6: Passing
- Python 3.7: Passing