Added option to not require touch before auto-dismiss is queued

By default, the undo dialog will only dismiss once the user touches the screen. This is to allow the user to 'acknowledge' that the removal has been made and can be undone. 

This change allows this functionality to be switched off through a public method when initialising SwipeToDismiss. Example usage:

ListView listView = // ... (findById or getListView)
SwipeDismissList.OnDismissCallback callback = // .. see below
UndoMode mode = // .. see below
SwipeDismissList swipeList = new SwipeDismissList(listView, callback, mode);
swipeList.setRequireTouchBeforeDismiss(false); // <-- NEW