This PR removes the broken and disabled coverage reporting that previously used coveralls and moves to using codcov.io. This is worthwhile because coveralls was not scaling well for several reasons:
Often the service would timeout so the post of data would fail
The cpp-coveralls tool breaks with llvm > 3.5 (not found a solution here, so moving to codecov works around this).
This PR removes the broken and disabled coverage reporting that previously used coveralls and moves to using codcov.io. This is worthwhile because coveralls was not scaling well for several reasons:
Closes #222