some problems with transfer options

simple_fields_for don't passed options and it's created some problems like this:
ryanb/nested_form#219
ryanb/nested_form#226

because if wrapper option is false, then wrapper not transfered

lib/simple_form/action_view_extensions/builder.rb

@@ -194,7 +194,7 @@ def collection_check_boxes(attribute, collection, value_method, text_method, opt
       #   end
       def simple_fields_for(*args, &block)
         options = args.extract_options!
-        options[:wrapper]  ||= self.options[:wrapper]
+        options[:wrapper] = self.options[:wrapper] if options[:wrapper].nil?
         options[:defaults] ||= self.options[:defaults]
 
         if self.class < ActionView::Helpers::FormBuilder