title: Detect mouseUp on stage
body: <p>Is there a way to check the method that has been attached to the stage?</p>
  
  <p>I have stage as global.. and need to fire some function in a object on mouseup...
  Now it fires 2 or 3 depending how many objects i add..</p>
  
  <p>I need something like..</p>
  
  <p>if($.stage.hasEventListener(MouseEvent.MOUSE_UP, this.mouseUp) === false){
   $.stage.addEventListener(MouseEvent.MOUSE_UP, this.mouseUp);
  }</p>
  
  <p>Or a better way to handle this?</p>