Fix exception caused when marshalling models

lib/ioki.rb

@@ -34,5 +34,13 @@ def config
     def configure
       yield(config)
     end
+
+    def deprecator
+      @deprecator ||= if defined?(Rails)
+                        ActiveSupport::Deprecation.new('1.0', 'Ioki')
+                      else
+                        Kernel
+                      end
+    end
   end
 end

lib/ioki/model/base.rb

@@ -340,15 +340,7 @@ def attribute_deprecated?(attribute)
       end
 
       def deprecation_warning(message)
-        if defined?(Rails)
-          deprecator.warn(message)
-        else
-          warn message
-        end
-      end
-
-      def deprecator
-        @deprecator ||= ActiveSupport::Deprecation.new('1.0', 'Ioki')
+        Ioki.deprecator.warn(message)
       end
     end
   end

lib/ioki/railtie.rb

@@ -8,5 +8,9 @@ class Railtie < ::Rails::Railtie
     ActiveSupport.on_load(:action_mailer) do
       add_delivery_method :ioki, Ioki::Mailing::Mailer
     end
+
+    initializer 'ioki.deprecator' do |app|
+      app.deprecators[:ioki] = Ioki.deprecator
+    end
   end
 end