title: Progress of UIPageViewController
body: <p>I would like to receive updates from the uipageviewcontroller during the page scrolling process. I want to know the transitionProgress in %. (This value should update when the user move the finger in order to get to another page). I'm interested in the animation progress from one page to another, not the progress through the total number of pages.</p>
  
  <p>What I have found so far:</p>
  
  <ul>
  <li><p>There is a class called <a href="https://developer.apple.com/library/ios/documentation/UIKit/Reference/UICollectionViewTransitionLayout_class/Reference/Reference.html" rel="noreferrer">UICollectionViewTransitionLayout</a> that have the property corresponding to what I am looking for, "transitionProgress". Probably uipageviewcontroller implement this method somehow?</p></li>
  <li><p>I can call the following method on the uipagecontroller but I only get 0 as result! </p>
  
  <p>CGFloat percentComplete = [self.pageViewController.transitionCoordinator percentComplete];</p></li>
  </ul>