module ActionController::Rendering

Override render_to_string because body can now be set to a Rack body.
--
instead of setting `self.response_body`.
Similar to #render, but only returns the rendered template as a string,

def render_to_string(*)
  result = super
  if result.respond_to?(:each)
    string = +""
    result.each { |r| string << r }
    string
  else
    result
  end
end