sole/tween.js — pull request #40 by egraether (2012-04-09 00:00:15+00:00)
Title: made .to() values dynamic 2.0

adapted from pull request #16 from @jeromeetienne

There was already a long discussion and I still think having dynamic values is really useful.

The benefit of this update using a short metaphor:

```javascript
var rabbit = { x: 0, y: 0 };
new TWEEN.Tween( rabbit ).to( { x: 100, y: 100 }, 1000 ).start();

var fox = { x: 100, y: 0 };
new TWEEN.Tween( fox ).to( rabbit, 1000 ).start();
```

The fox follows the moving rabbit, without the tween being updated separately.

**pros:**

* more functionality for the user
* less code
* removes `_valuesDelta`
* no change in performance

**cons:**

* `.to()` can only be called once per tween, a second call would overwrite the first.

Any concerns about this, or something that I missed?