exclude twig verbatim blocks from twig formater tests

this patch exclude twig verbatims block from block test, it's allow you now to add code blocks in your markdown posts with ` {% block blockname %}{% endblock %}` inside without errors.

For example if you need to add this code block in a markdown post, it's now possible.

    {% verbatim %}
    <!DOCTYPE html>
    <html lang="fr">
    <head>
        <meta charset="UTF-8">
        <title>{{ site.title }}</title>
        <link rel="stylesheet" href="//netdna.bootstrapcdn.com/bootstrap/3.1.1/css/bootstrap.min.css">
    </head>
    <body class="container">
        <header>
            <h1>{{ site.title }}</h1>
            <h2>{{ site.subtitle }}</h2>
        </header>
        <div id="content">
            {% block content %}{% endblock %}
        </div>
    </body>
    </html>
    {% endverbatim %}