added support for usage along with UINavigationController (only tested top mode)

I'm using this classes along side with a UINavigationController in top mode and I had problems both with the NavigationController itself and with the Title Bar in iOS 7+. Therefore I put some changes to it in case that a NavigationController is apparent and iOS 7+ is used. Also I added a white background color due to some problems during Animations when NavigationController is used and didn't put a check for NavigationController for that for a more consistent look and behavior in all cases.