refactor workflow to install from build configuration and use `pytest` and `tox`

[zacharyburnett]

This PR refactors the workflow CI to run on push to master or on a pull request, and additionally uses tox to run lint / build checks before running tests with pytest-xdist.

blocked by #217:

AttributeError: module 'numpy' has no attribute 'int'. Did you mean: 'inf'?

[codecov[bot]]

Codecov Report

:exclamation: No coverage uploaded for pull request base (master@d4e1c66). Click here to learn what that means. Patch has no changes to coverable lines.

Additional details and impacted files

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