Raw tag

A tag which apparently has just been added to django 1.3.

I just came across the scenario where I needed to render jquery-tmpl templates (or similar) within a template of mine. As you may guess jquery-tmpl syntax messes with the tags and variables in h2o templates.

Hence the need for `{% raw %}` and corresponding `{% endraw %}` tags.

Anything within these two tags will not be parsed and passed on as though they were plain text all along.

Example:
```
Hello, {{ name }}
{% raw %}
<script type="text/x-tmpl">
{% for (cat in cats) { %}
    <span>{%=cat.name%}</span>
{% } %}
</script>
{% endraw %}
```
When rendered with `array('name' => "Bob")` produces as expected:
```
Hello, Bob
<script type="text/x-tmpl">
{% for (cat in cats) { %}
    <span>{%=cat.name%}</span>
{% } %}
</script>
```