add tests for yoyo and repeat with nested objects (make changes if needed).

[trusktr]

With the merge of #539 and #541 we got support for animating properties inside nested object or arrays.

But we haven't tested repeat or yoyo with this yet. We should add some tests and and example, and update the implementation if needed.

[trusktr]

Instead of ensuring we support more complexity, we will move towards decoupled features with separation of concerns, for example making a Timeline for managing multiple tweens instead of overloading a single class with many features in an unmanageable way.

So, we'll close this in favor of moving in that direction, and features like yoyo and repeat will be separate concepts on their own, hence this problem goes away, and things will be simpler.