title: moving a view under finger
body: <p>I have a view-chain; the first view is in the second, the second is in the third and so on.
  I want to move the top most view under my finger and I did some logics to handle this in touchesBegan:touchesMoved:...
  The problem is that each view has different gestures and if I try to move the top most view, the views behind it also respond to the moving. Is there any way to disable the gesture except the top most view when I am trying to move it?</p>
  
  <p>Also I do not want the top most view to go outside the border of its immediate parent view, and I did some logics in the touchesMoved: to reset the center or the top-most view. The effect is not good as this approach allows the view to go outside, but will move it back once it went out.</p>