ADD : Update Model with favoritebooks methods

Model/IUserLibraryManager.cs

@@ -21,6 +21,8 @@ namespace Model
         Task<bool> AddToFavorites(string bookId);
         Task<bool> RemoveFromFavorites(Book book);
         Task<bool> RemoveFromFavorites(string bookId);
+        Task<Tuple<long, IEnumerable<Book>>> GetFavoritesBooks(int index, int count);
+
 
         Task<Book> UpdateBook(Book updatedBook);
 

Stub/UserLibraryStub.cs

@@ -421,5 +421,10 @@ namespace Stub
         {
             return Task.FromResult(Tuple.Create(Contacts.LongCount(), Contacts.Skip(index * count).Take(count)));
         }
+
+        public Task<Tuple<long, IEnumerable<Book>>> GetFavoritesBooks(int index, int count)
+        {
+            return Task.FromResult(Tuple.Create(Favorites.LongCount(), Favorites.Skip(index * count).Take(count)));
+        }
     }
 }