Regression: Children are not being updated by their parent actors

[kamranayub]

Steps to Reproduce

1. Create an Actor
2. Create another Actor
3. Add the second actor to the first
4. Add logic to the second actor's update method
5. Verify when game starts that the logic in the second actor's update is never called

Expected Result

Children actors should participate in the update loop. This is a regression.

Actual Result

Child actor's update is never called

Proposed Changes

Add this to the end of Actor.update:

// Update child actors
for (var i = 0; i < this.children.length; i++) {          
  this.children[i].update(engine, delta);          
}

[eonarheim]

:( mega sad