title: UIScrollView cancels UIPageViewController gestures when scrolling
body: <p>I have a <code>UIPageViewController</code> that handles turning the pages of my "book".  However, each book page is a <code>ViewController</code> with a <code>UIScrollView</code> as a <code>subview</code>.  The <code>UIScrollView</code> is only able to scroll vertically due to the <code>contentSize</code>.  The problem is that while the user scrolls the <code>scrollview</code> vertically, as the <code>scrollview</code> is still scrolling/decelerating the user can not turn the page.  A very easy way to see this is to scroll the page and then try to tap the edge of the view.  This would normally change the page, and it does change the page when the <code>scrollview</code> is not moving.  However, when it is moving, the tap causes the scrollview to stop moving instead of turn the page.  </p>
  
  <p>How do I cancel the <code>scrollviews</code> gestures if the <code>UIPageViewController</code> is trying to use the gesture to turn the page by tapping or panning the page to cause the page turn animation?</p>
  
  <p>For an example of the behavior I want to achieve, check the Twitter's official client on the iPhone.
  It's possible to swipe from Timeline to Discover while the feed is still decelerating from scrolling.</p>