title: Django datatable view related fields
body: <p>I am getting confused by this one. I am using <a href="http://django-datatable-view.appspot.com/" rel="nofollow">http://django-datatable-view.appspot.com/</a> to show data from models. However I get Error: "'tuple' object has no attribute 'replace'. Is it some model type issue or conversion issue?</p>
  
  <p>My lists </p>
  
  <pre><code>class CustomerList(BaseDatatableView):
      model = Profile
  
      columns = [("id", 'user__id'), ("name", 'customer__name'), 'abn', 'street', 'suburb', 'post_code', 'state', 'mobile']
      order_columns = [("id", "user__id")]
      max_display_length = 500
  
      def render_column(self, row, column):
          pprint.pprint(globals())
          pprint.pprint(locals())
          if column == 'mobile':
              return str(row.mobile)
          else:
              return super(CustomerList, self).render_column(row, column)
  
      def get_initial_queryset(self):
          return Customer.objects.filter(client_id=self.request.user.profile.client.id)
  </code></pre>
  
  <p>My models</p>
  
  <pre><code>class Customer(models.Model):
      name = models.CharField(max_length = 100)
      client = models.ForeignKey(Client)
      date_created = models.DateField(auto_now_add = True, null=True, blank=True) 
      history = HistoricalRecords()
  
      def __unicode__(self):
          return self.name
  
  class Profile(models.Model):
      user = models.OneToOneField(
          User,
          primary_key=True,
          related_name='profile'
      )
      abn = models.CharField(max_length=11,help_text = "Australian Business Number")
      street = models.CharField(max_length=100)
      suburb = models.CharField(max_length=100)
      client = models.ForeignKey(Client,blank=True,default=1,null=True)
      customer = models.ForeignKey(Customer,blank=True, null=True)
      history = HistoricalRecords()
  
      post_code = models.CharField(max_length=100)
      state = models.CharField(max_length=10)
      country = models.CharField(max_length=100, default = 'AU')
      points = models.DecimalField(max_digits=14, decimal_places=4,default=0)#precision to 2 decs as the prices [will need to be rounded down]
      mobile = PhoneNumberField(blank=True, null=True)
      avatar = models.CharField(max_length=255,default="",blank=True)
      invite_token = models.CharField(max_length=128,default="",blank=True)
  
      def __unicode__(self):
          return self.user.get_full_name()
  </code></pre>