Handle table views where contentInset.top != 0 which is often the case in iOS7

I've been trying this great little class with iOS7 (beta3) for a new project I'm working on. In iOS7, UITableViews extend up under the translucent navigation bar and status bar and therefore have a contentInset set where top is not 0 (it's usually 64, which is the height of the nav bar, 44 + the height of the status bar, 20).
This class didn't handle the case where the UITableView had a contentInset.top other than 0 (regardless of whether running in iOS7 or not). These changes made the class handle a top content inset properly.