title: Hyperlink to not editable foreign key filed in django admin
body: <p>There is a thing I have a model with ForeignKey/OneToOneFiled to other model (with editable is set to False) like follow:</p>
  
  <pre><code>class Campus(TimeStampedModel, StatusModel):
      # other fields
  
      gallery = models.ForeignKey(Album, editable=False, related_name='campus')
  </code></pre>
  
  <p>What I want to achieve is to have Campus admin page with link to the gallery (not editable field, just link). So there is a trick to do that provided in django documentation <a href="https://docs.djangoproject.com/en/1.6/ref/contrib/admin/#django.contrib.admin.ModelAdmin.readonly_fields" rel="nofollow">link here</a>.</p>
  
  <p>And I have done that:</p>
  
  <pre><code>class CampusAdmin(admin.ModelAdmin):
      readonly_fields = ('gallery',)
  
      def gallery(self, instance):
          print 'got here'
          return '&lt;a href="%s"&gt;%s&lt;/a&gt;' % ('/test/url', 'Test name')
  
      gallery.short_description = "Gallery"
      gallery.allow_tags = True
  
  
  admin.site.register(Campus, CampusAdmin)
  </code></pre>
  
  <p>As a result I have visible gallery field in django admin but it is just a text (gallery name) not a hyperlink as I expect to be.</p>
  
  <p>The gallery function is actually never called, as I checked.</p>
  
  <p>Does anyone know what am I doing wrong ?</p>