title: BindView and UnbindVIew in Recycler Adapter
body: <p>Is there any way to find out when a view is being used for some other position in an adapter. For e.g. there are 10 positions. and View has been created for first 4 of them. When we scroll up, the first view will now be reused for item 5. I need to know the moment that particular view is not being used for item 1. 
  The use case is that, I am using observables inside the viewholder and need to unsubscribe at the right time. </p>