Add 'renderOnShutdownWithHead' function

If we use debugbar with Twig. There is possible that we have somewhat difficulty to implement this header.

Put the header with body, check if header is include or not. With this line :

        if ($count === 0) {
            echo $render;
        }
Merge pull request #101 from GuimDev/patch-1

Add 'renderOnShutdownWithHead' function