Events: QUnit logging system uses EventEmitter

Fixes #422.

Even though this is earmarked for `v2.0`, it is 100% backward compatible.

Critique away.  :wink::wine_glass:
 1. Standard EventEmitter behavior/API.
 2. Thinking ahead to Reporters, e.g. if Reporters become an event-driven interface, then we would need to remove event listeners if the Reporters (especially the default reporter) can be removed/disabled.