12.1.0

- Added isActive() method to all animation classes (TweenLite, TweenMax, TimelineLite, and TimelineMax)

- Added progress() and totalProgress() methods to TweenLite (they were already available in TweenMax, TimelineLite, and TimelineMax)

- Added a new "onlyActive" parameter to the getTweensOf() and killTweensOf() methods so that it's easy to find (or kill) only the active tweens of a particular target/object.

- Fixed several issues that could cause zero-duration tweens inside timelines to render incorrectly in very particular (and rare) scenarios

- Adjusted behavior of callbacks (and zero-duration tweens) in timelines so that if the playhead moves directly on top of the callback/tween when suppressEvents is true, it will execute callbacks on the following render (when the playhead leaves that spot). So callbacks will get triggered EITHER when the playhead arrives OR when it leaves that spot (not both).