[reproducibility] Package code and enable installation with pip

[cthoyt]

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The installation guide can be greatly reduce in complexity and length by packaging the code and making it pip-installable. This should probably be done after #7 and #8.

I've written a guide for scientists on how to do this https://cthoyt.com/2020/06/03/how-to-code-with-me-organization.html but I'd be happy to submit a minimal PR to get you started and help you understand what changed.