title: add link or any html tag to column in django-datatables-view
body: <p>I've got django-datatables-view looking like this:</p>
  
  <pre><code>class OrderListJson(BaseDatatableView):
      model = Flat
      columns = ['id', 'flat_price', 'flat_house.house_block.block_name']
      order_columns = ['flat_price', 'flat_house.house_block.block_name']
      max_display_length = 100
  
      def filter_queryset(self, qs):
          search = self.request.GET.get(u'search[value]', None)
          if search:
              qs = qs.filter(flat_price__lte=search)
          return qs
  </code></pre>
  
  <p>How to wrap <code>'flat_house.adress'</code> with <code>&lt;a&gt;</code> or any other html-tag? For example,<code>&lt;a href="{% url 'id' %}"</code>. Right now I only show the data from the column in a <code>&lt;td&gt;</code> tag.</p>
  
  <p>My html-template looks like this:</p>
  
  <pre><code>&lt;table id="datatabletest" class="table table-striped table-bordered" cellspacing="0"&gt;
              &lt;thead&gt;
                &lt;tr&gt;
                  &lt;th&gt;id&lt;/th&gt;
                  &lt;th&gt;price&lt;/th&gt;
                  &lt;th&gt;adress&lt;/th&gt;
                &lt;/tr&gt;
              &lt;/thead&gt;
              &lt;tfoot&gt;
                &lt;tr&gt;
                  &lt;th&gt;id&lt;/th&gt;
                  &lt;th&gt;price&lt;/th&gt;
                  &lt;th&gt;adress&lt;/th&gt;
                &lt;/tr&gt;
              &lt;/tfoot&gt;
            &lt;/table&gt;
  </code></pre>