Simple twilio decorator

Whilst developing with Django I noticed that the ```twilio_view``` decorator really dislikes my development environment (I'm using [ngrok](http://ngrok.com)). This is caused by the validation in the HTTP headers tripping over, rendering the decorator useless.

I could simple skip the decorator and return something like this:

```return HttpResponse(resp, mimetype='application/xml')```

However, django-twilio is supposed to make Twilio __easy__ with Django, so I decided to write a simplified decorator that works similarly to ```twilio_view``` but skips over the Twilio validation part.