Change singular to param_key in form_helper, param_key is now used for generating field names

Signed-off-by: NMikel Lindsaar <raasdnil@gmail.com>

actionpack/lib/action_view/helpers/form_helper.rb

@@ -306,11 +306,11 @@ def form_for(record, record_object = nil, options = nil, &proc)
           object = record_object
         when Array
           object = record.last
-          object_name = options[:as] || ActiveModel::Naming.singular(object)
+          object_name = options[:as] || ActiveModel::Naming.param_key(object)
           apply_form_for_options!(record, options)
         else
           object = record
-          object_name = options[:as] || ActiveModel::Naming.singular(object)
+          object_name = options[:as] || ActiveModel::Naming.param_key(object)
           apply_form_for_options!([object], options)
         end