Add extra offset when navcontroller is in a tabbar controller

[SamuraiZack]

There seems to be some offset issue when a viewcontroller is pushed from a navigation controller inside a tabbar controller. This will fix the center offset and will only work correctly if the sloppy swiper delegate is used and returns false on animatorShouldAnimateTabBar.

[zzzworm]

This patch has bugs, will made the navcontroller in tabBarcontroller offset wrong