use to_prepare for Rails 2

Author: nightpool

lib/attr_encrypted/adapters/active_record.rb

@@ -133,7 +133,7 @@ def method_missing_with_attr_encrypted(method, *args, &block)
     end
   end
 
-  ActiveSupport.on_load(:active_record) do
+  Rails.configuration.to_prepare do
     extend AttrEncrypted
     extend AttrEncrypted::Adapters::ActiveRecord
   end