Fix node-coveralls to make it better usable as a library

[pimterry]

Currently we have to override coveralls.getOptions to ensure it doesn't try and read from process.argv, because that's what it does by default.

That's not a good default; node-coveralls should probably be updated to provide a library API that doesn't make these assumptions, and a simple command-line wrapper that does, so we can use the library API directly and safely here.