remove namedRoutes cache
remove namedRoutes cache

Updated based on feedback / conversation on pull request
slimphp/Slim,akrabat/Slim,iinux/Slim,foxyantho/Slim,RealSelf/Slim,dopesong/Slim,Sam-Burns/Slim,juliangut/Slim,JoeBengalen/Slim,iinux/Slim,iinux/Slim