Updates code and fixes bugs with getting child views and existing PullToRefreshAttachers

Pull Request accomplishes the following:

-Adds helper method to allow the constructor of the PullToRefreshAttacher to remove a previous implementation from the ViewGroup, if present. Previous code merely threw exception as "returning existing instance" functionality is not built. 

-Fixes deletion error when pulling child views from old ViewGroup into new DecorChildLayout.

-Fixes bug where original instance (before rotation) would cause refreshing view to be behind the Android Status bar. 

-Removes duplicated and deprecated code