title: IOS: add imageview in a scrollview to have zoom
body: <p>I want to set a UIImageView with a <code>UIImage</code> and put this imageview inside a <code>UIScrollView</code> to obtain a zoom of this image;
  and I want this <code>UIImageView</code> and <code>UIScrollView</code> to fit in the rect at the center of the view...is it possible?</p>