Vertical paging

[pvn-anh-pham]

This lib is awesome! I already integrated this lib into my app but it much more awesome if it support vertical paging. For now some Image source can be height > n*width, so I think it is better to support vertical paging so user can view that kind of image at full screen. When they scroll down to the end of image, it will goto the next one instead of swipe right/left

I hope this can be next improvement Thank