iOS UITabBar (controller) inspired by Google's Paper Material Design. BFPaperTabBarController is a subclass of UITabBarController that behaves much like the new paper tab bar from Google's Material Design Labs. All animation are asynchronous and are performed on sublayers. BFPaperTabBarControllers work right away with pleasing default behaviors, however they can be easily customized! The tap-circle color, background fade color, tap-circle diameter, underline color, and underline thickness are all readily customizable via public properties.