NavigationBar ignores existing contentInsets

[pinkable]

HidingNavigationBar works perfectly apart from this one point.

Before implementing:

After implementing:

The navigation hiding functionality works fine but I am losing my initial contentInset values.

tableView.contentInset = UIEdgeInsets(top: 8, left: 0, bottom: 0, right: 0)

Would be a great improvement.

I've used a hack in the meantime:

    private func updateContentInsets() {
        let navBarBottomY = navBarController.view.frame.origin.y + navBarController.view.frame.size.height + 8

[tristanhimmelman]

If you have time to make a pull request for this that would be great!