Ignore {% %} patterns

Hi,

I'd like to be able to specify the regexp for substitutions.
Currently, I'm using {%= %}. Eg. {%= name %}
I would expect that any other pattern is ignored. However, {% name %} will be replaced by the empty string - not at all what I expected.

This is the result of a quick test:

``` bash
{%= name %}
{% name %}
{{% name %}}
<%= name %>
```

will be replaced by

``` bash
MyProject

{}
<%= name %>
```

The second and third line don't seem to be right. They should be ignored.

The original use case I had was scaffolding django templates, that also use the {% %} syntax. So, I'd like to be able to ignore those completely.

Any idea how to do that?