title: Displaying the model's__unicode__ in django admin
body: <p>I would like to display the model's username in Django Admin interface but not very sure how to do it..</p>
  
  <pre><code>The models.py:
  
      class Adult(models.Model):    
          user = models.OneToOneField(User)
          fullname = models.CharField(max_length=100,
                                      blank=True)
          def __unicode__(self):
              return self.user.username
  
  Admin.py:
  
      class AdultAdmin(admin.ModelAdmin):
          list_display = ('??', 'Student_Name',)
          search_fields = ['??',]
  
      admin.site.register(Adult, AdultAdmin)
  </code></pre>
  
  <p>What should go inside the ?? above ? I would like to display the unicode or the self.user.username? How do i do it? Need some guidance...</p>