Turn library into a simple ScrollListener

[davideas]

First, very good idea you had 👍

I analysed your 3 classes, and I think you can just expose 1 simple ScrollListener and 1 interface for the adapter (you already have abstract methods there), without extending RecyclerView which can be a big limitation for others. Possibly but not sure, also an interface for the LayoutManager to not exclude all thirds libraries out there!