Code coverage reporting

[caryan]

if we have unit tests we should know how much we're testing. Since the unittests require a device I don't think we'll be able to use coveralls.io but we should manually run it once in while

[blakejohnson]

Well, coveralls.io is just a means to display coverage data. If we setup a GitLab CI worker with access to our development APS2 system, then we should be able to post that data back to coveralls.