remove Rails 3 :parent_builder work-around

lib/formtastic/form_builder.rb

@@ -79,12 +79,7 @@ def self.configure(name, value = nil)
     #
     # @todo is there a way to test the params structure of the Rails helper we wrap to ensure forward compatibility?
     def semantic_fields_for(record_or_name_or_array, *args, &block)
-      # Add a :parent_builder to the args so that nested translations can be possible in Rails 3
-      options = args.extract_options!
-      options[:parent_builder] ||= self
-
-      # Wrap the Rails helper
-      fields_for(record_or_name_or_array, *(args << options), &block)
+      fields_for(record_or_name_or_array, *args, &block)
     end
 
     def initialize(object_name, object, template, options)