Testing improvements

[PhillipNordwall]

Testing improvements through the addition of

• PyTest
• Mocking
• Unit tests

would be good

[reillysiemens]

The tests that I added in #11 are a good demonstration of what I'm looking for if you still want to lend a hand, @PhillipNordwall.

Test coverage is currently sitting at 41%. I'd like to bump that up by testing all but the CLI (the cli function) for now. That will be its own can of worms and I'll likely move it out into its own module when I get around to refactoring.

[reillysiemens]

We're up to 61% on master now and all but the CLI is tested. Further testing improvements should wait until after the CLI has been refactored into a separate module.