Apply transforms when checking if binding should be synced.

Previously, sync would only check that the value had changed. Now it will
also apply transforms and see if the transformed value changed.

For example:
```javascript
A = SC.Object.create({
  abc: undefined
});
B = SC.Object.create({
  def: SC.Binding.oneWay('A.abc').transform(function (value, binding) {
    if (value === undefined) {
      return 'A valid value';
    } else {
      return value;
    }
  })
});
```

In this example, B.def would initially be undefined, not 'A valid value', since the transform would be ignored when determining if the value should be initially synced.