add note in README - if displayed by pushViewController()

[flexund]

I had a huge issue when the AnimatedPagingScrollViewController was displayed in a navigation controller. The scrollView was behaving strange as if the contentView was too big and vertical scrolling was enabled.

This was due to the ViewController I used to subclass AnimatedPagingScrollViewController had the Adjust Scroll View Insets enabled. When disabled it worked just fine.