Add back emit() for backwards compatibility.

Also, it's not clear to me why the switch to emitEvent() was made.  I'd be interested in understanding that if it will get this PR accepted.

It's also not clear to me why emitEvent expects a single array argument instead of using arguments/splice to pass its arguments on to the listeners.  What's the reasoning there?  If I'm missing something and this PR isn't desirable, please let me know.