Add tests

[justmobilize]

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[justmobilize]

@FoamyGuy w00t! Ask and you shall receive! This uses actual requests to compare the payload sent.

[FoamyGuy]

@justmobilize Awesome! Thank you 🎉

I committed a few tweaks:

• changed copyright name and year from the copy/pasted ones to you / current.
• moved requests to optional_requirements.txt instead of requirements.txt. CPython requests is needed to run the tests, but isn't needed for anyone who is just installing adafruit_requests via pip to use as normal instead of running the tests.
• added timeouts to the cpython_requests.post() calls. Locally my pylint was failing due to those not having timeouts, this way the test cannot get stuck indefinitely.