Non-enumerable properties of the source object can now be tweened. Values in the destination object must still be enumerable in order for them to be tweened.
Added an "end" function which is known to randomly fail. Don't use it until we fix that!
Fixed the timestamp calculation for node.js.
Removed some redundant start-value copying.
Removed excess arguments to parseFloat.
Fixed a possible issue with transpilers and the performance.now polyfill.