Record coverage to point out untested code

[colinnewell]

A fair bit of the code is untested and that ought to be rectified. To help with that coverage ought to be generated and made obvious.

This ideally should take both the go tests and the e2e tests into consideration. The latter can be done with a specially built binary, and then combined to produce an overall coverage report.

For bonus points prevent a reduction in coverage. It might be that coveralls (the service) is the answer, or some other mechanism.