render/func.go
func (e *Engine) Func(s string, fn RendererFunc) Renderer {
	return Func(s, fn)
}
func (e *Engine) Func(s string, fn RendererFunc) Renderer {
	return Func(s, fn)
}
// Func renderer allows for easily building one of renderers
// using just a RendererFunc and not having to build a whole
// implementation of the Render interface.