Support {% verbatim %} template tag as `- verbatim`

[folz]

A template that uses the {% verbatim %} template tag as - verbatim raises a TemplateSyntaxError: "Unclosed tag 'verbatim'. Looking for one of: endverbatim."

Sample template that fails:

- verbatim
  %h1= page_title

Everything works if I wrap the block in non-Haml {% verbatim %} tags, like so:

{% verbatim %}
  %h1= page_title
{% endverbatim %}

Output:

<h1>{{ page_title }}</h1>

[Naddiseo]

It's easy enough to add:

from hamlpy import nodes as hamlpynodes
hamlpynodes.TagNode.self_closing.update(verbatim = endverbatim)

[maxvyaznikov]

But what about all other 3rd-party tags? - From https://pythonhosted.org/django-templateaddons/template_tags/assign.html for example.