title: Can Haystack filter by a geodjango PointField?
body: <p>I want to be able to use django-haystack to do full text searches on a model.  This model uses a PointField to store coordinates.  I want to filter the results of a search based on the distance from a point.  Is this possible with Haystack?  Is there a better way to do this?</p>
  
  <pre><code>from django.contrib.gis.db import models
  
  
  class Listing(models.Model):
      name = models.CharField(max_length=255)
      description = models.TextField()
      location = models.PointField()
  </code></pre>