Do not tween inherited properties

I'm using TweenJS with Three.js and this is very annoying.
For example, I can't easily operate with THREE.Vector instances because of large amount of their inherited properties. Simple "Tween.get(vector1).to(vector2)"-pattern is inefficient for now.

a._cloneProps = function(a) {
    var b = {};
    for (var c in a) // if (a.hasOwnProperty(c)) would be nice here
        b[c] = a[c];
    return b
}

[gskinner]

Interesting. Totally see the use case here of passing a typed DTO. I am a little concerned that in some cases people will want the inherited property to come through, and it will be confusing why it doesn't.

As an aside, the actual implementation would require a check in the for...in loop(s) in _appendProps. It's also complicated by the fact that we now delete properties of the props object if a plugin tells us to ignore it.

I'm going to take a look at this to see if I can identify a good solution. In the interim, you could just run the DTO through a simple clone method to output a generic object with the values you want.

[gskinner]

I addressed this issue in 3d23ded, feedback welcome.