CircleCI hangs when mocha isn't force-exitting tests

[ryanhallcs]

As of mocha >= 4, tests do not auto-exit without a flag - orphaned async/unresolved promises/open connections will force a test suite to remain running indefinitely

Jackrabbit's mocha lib is now at 6 and the mocha options in package.json set the force-exit flag to true to work around the hanging (but passing) tests in CircleCI

I have not been able to replicate in docker-compose or locally (tests exit). This issue is to track cleaning up the tests to close out.

A good example is this test: https://github.com/pagerinc/jackrabbit/blob/master/test/jackrabbit.test.js#L58-L78 - even after adding the .close() on the connection, the test will hang in mocha

[ryanhallcs]

closed in #64