unit tests

as this is now open source and people are contributing PRs, could we please have a test suite in the repo too so that we can test changes against a known / comprehensive suite of tests.

[drew-gross]

We have a test suite! Clone the repo and run npm test. The tests are run on every PR as well, and we have checks to make sure the code coverage doesn't decrease. Check out an example here: https://codecov.io/github/ParsePlatform/parse-server?ref=05fb117aac1c2833d43bd7b284442e63b8f52580

We would also be super excited to see PRs adding more tests to existing features!

Thanks!