Emit events

[sole]

As discussed in tweenjs/tween.js#195 (comment) - it would avoid polling and weird status, and probably help saving battery.

[dalisoft]

@sole, Here you can check https://gist.github.com/dalisoft/8b87519bbc54d029f7a6a576673661ec
With some of years, i have some exp with performance, power saving and make simple and easier for users.
Most of them, you('re) teached me. Maybe you like this or no. Anyway, i want tween.js always up-to-date with new cool features.
Thanks,
@sole and All contributors and users.
Good luck for your projects and happy Tweening 👍

[dalisoft]

Already implemented ;)