macaron.go
func (m *Macaron) Action(handler Handler) {
	handler = validateAndWrapHandler(handler)
	m.action = handler
}
func (m *Macaron) Action(handler Handler) {
	handler = validateAndWrapHandler(handler)
	m.action = handler
}
// Action sets the handler that will be called after all the middleware has been invoked.
// This is set to macaron.Router in a macaron.Classic().