The private method with_callbacks on the Cart class now returns the c…

…lass object when successful.

lib/active_cart/cart.rb

@@ -184,6 +184,8 @@ def with_callbacks(type, item, quantity, options, &blk)
 
       @storage_engine.send("after_#{type}".to_sym, item, quantity, options) if @storage_engine.respond_to?("after_#{type}".to_sym)
       item.send("after_#{type}".to_sym, quantity, options) if item.respond_to?("after_#{type}".to_sym)
+
+      self
     end
   end
 end