Merge pull request #62 from SamMarkGoldman/no_active_record

eliminate ActiveRecord as a dependency for errors

Author: tiagopog

lib/jsonapi/utils/response/formatters.rb

@@ -22,7 +22,7 @@ def jsonapi_format_errors(data)
         private
 
         def active_record_obj?(data)
-          data.is_a?(ActiveRecord::Base)|| data.singleton_class.include?(ActiveModel::Model)
+          defined?(ActiveRecord::Base) && (data.is_a?(ActiveRecord::Base) || data.singleton_class.include?(ActiveModel::Model))
         end
 
         def build_response_document(records, options)