Add Test Framework

[WilsonGregory]

Changes

• add the pytest framework for writing automated unit tests. You can add a file like test_whatever.py to the tests folder, and it will automatically run the functions in the that method
• added an example of a unit test file in tests. This is a pretty trivial example, but the idea is that if you are making some larger logic changes, you can write tests and make sure that they work before and after the feature changes. This doesn't replace testing on larger datasets in a more realistic fashion, but it will make it easier to catch smaller errors
• later we can have the tests run automatically when you create a pull request

Tests

• ran the tests

Doc Changes

• update readme to include pytest installation

[beelze-b]

I think this is great. Adding robustness and tests for the (de)serialization of data, models, results, etc is super good.

I am curious to your thoughts on what parts of the code most need tests. Some of the code needs reformatting, and adding tests to those sections might be imperative. Or they could also be unnecessary if we end up discarding that part of the code.

[WilsonGregory]

I think the tests will be most useful to me just to sanity check that I didn't break the existing code when doing a refactor or adding some feature to an existing function. So I just plan on writing tests as I go along for stuff I am changing. So I don't think there are critical areas in the codebase that need tests written right now.

The one place where it might be good to write a few tests is the main MarkerMap class functionality. Maybe just a few to ensure that the combination of args makes sense.