More thorough testing

[geraintwhite]

Currently we only test listener.js Listener.hook.

[geraintwhite]

I've added tests for the rest of Listener.prototype.

[geraintwhite]

We should still test server.js and parser.js.

[olls]

Is this useful? https://github.com/michaelrhodes/tape-catch

[geraintwhite]

Currently we only have unit tests for build-manager.js with test coverage of three files.