do not generate id method (was for 1.8 only)

see https://github.com/rails-api/active_model_serializers/issues/127
for original motivation

lib/generators/serializer/serializer_generator.rb

@@ -13,9 +13,6 @@ module Rails
       end
 
       private
-      def generate_id_method
-        RUBY_VERSION =~ /1\.8/
-      end
 
       def attributes_names
         [:id] + attributes.select { |attr| !attr.reference? }.map { |a| a.name.to_sym }

lib/generators/serializer/templates/serializer.rb

@@ -4,16 +4,5 @@ class <%= class_name %>Serializer < <%= parent_class_name %>
 <% association_names.each do |attribute| -%>
   has_one :<%= attribute %>
 <% end -%>
-<% if  generate_id_method %>
-
-  # due to the difference between 1.8 and 1.9 with respect to #id and
-  # #object_id, we recommend that if you wish to serialize id columns, you
-  # do this. Feel free to remove this if you don't feel that it's appropriate.
-  #
-  # For more: https://github.com/rails-api/active_model_serializers/issues/127
-  def id
-    object.read_attribute_for_serialization(:id)
-  end
-<% end -%>
 end
 <% end  -%>