Fix the build on 1.8.7 :trollface:

lib/active_model/serializer.rb

@@ -504,9 +504,7 @@ module ActiveModel
       hash
     end
 
-    def read_attribute_for_serialization(name)
-      send name
-    end
+    alias :read_attribute_for_serialization :send
   end
 end
 

test/test_helper.rb

@@ -34,3 +34,7 @@ ActiveSupport::TestCase.class_eval do
     @routes = ::TestHelper::Routes
   end
 end
+
+class Object
+  undef_method :id if respond_to?(:id)
+end