Add new NatGeo-like transition

Add transition inspired by [National Geographic's City Guide](https://itunes.apple.com/us/app/city-guides-by-national-geographic/id592453480?mt=8). 

It's basicaly an adoptation of [MHNatGeoViewControllerTransition](https://github.com/michaelhenry/MHNatGeoViewControllerTransition/) to iOS7 APIs.