Update SlideNavigationController with helper function - removeAllMenu…

[foreza]

An issue a client of mine faced was with loading interstitial ads on top of the root controller.

The current library doesn't present a way to clean up the menu from the superview.

This function is only invoked when we switch from the left -> right menu, or vice versa.

Provided a public method that can be invoked in such circumstances that will clean up either the left or right menu (whichever is active) as well as reset the lastRevealedMenu