Enabled tweak view controller presentation anywhere in hierarchy.

This fixes FBTweakViewController not being presented if rootViewController has presented another view controller, because its view is not in the window hierarchy. The error I was getting was:

_Warning: Attempt to present <FBTweakViewController: 0x914ffd0> on <UITabBarController: 0x8c7bc70> whose view is not in the window hierarchy!_

It also enables presentation of FBTweakViewController when we are deeper into the hierarchy.