optimize emit method, remove split/map/callback and allocations

[ngokevin]

Description:

Removes the multiple-event-emit support, which I never used and did not even know about.

Changes proposed:

• Don't allocate an object if detail is undefined, allow it to be falsy.
• For each child load, don't allocate object.
• Remove multiple-event support, saving a string split, map, and callback on each emit.