Github Actions `continue-on-error` gives unintended results

[ekilmer]

We want to replicate Travis's "allowed-failure" feature on Github Actions, but it looks like it isn't implemented according to this link https://github.community/t5/GitHub-Actions/continue-on-error-allow-failure-UI-indication/m-p/37033#M2780. master shows a green color status even if the tests fail.

The bigger problem, aside from master builds showing Green even if they fail, is that the master build does not run until completion if the PyPI build fails. I'm not entirely sure how to fix this. Fixed with fail-fast: false in #39