右滑返回手势:基于SloppySwiper的代码与storyboard的demo
storyboard方式：在storyboard的NavigationController拖放一个：Object，修改Class为SloppySwiper，在SloppySwiper的“Show the connections inspector”上：Outlets与“Referencing Outlets”分别指向NavigationController与NavigationController的delegate。
SloppySwiper源码地址 - https://github.com/fastred/SloppySwiper