ReferenceError: Can't find variable: Rectangle
Rectangle is not exposed to the global space so `parent.newGroup({"frame": new Rectangle(0, 44, 100, 44)});` fails.

Is it safe to add this to the top of `Rectangle.js`?

``` javascript
function _Rectangle(x, y, width, height) {
  return new Rectangle(x, y, width, height);
}

__globals.Rectangle = _Rectangle;
```

This fixes the issue, but I'm not sure if there should be a global object named `Rectangle`, what do you guys think?
