iOS 7 Navigation Bar Appear Over The Views
A lot of elements has changed in iOS7, they have introduced new properties that lets you adjust the layout behavior as in previous versions of iOS. The Navigation Bar appears over the views now because a default setting has changed, to address this issue use this line in the viewDidLoad()
self.edgesForExtendedLayout = UIRectEdgeNone;
This will automatically account for the extra space the navigation bar takes up.