Increase code coverage to 100%

[nolanlawson]

Since we can test in-memory in Node now, this should be pretty easy to use with Istanbul/Coveralls.

[nolanlawson]

This is kinda ambitious for a first-timer issue, but here's the general idea of how I would approach this:

• Run the coverage tests (npm run coverage), then look at the coverage reports in a browser (coverage/lcov-report/index.html) and see which parts are red
• Run the browser tests (npm run test-zuul-local) and see if there's a code path that would lead to the red parts. If so, try to write a test that passes through that red part. If not, add a /* istanbul ignore */ directive or remove it entirely if it seems safe to do so.