Added usage docs.

docs/_build/html/search.html

@@ -63,6 +63,10 @@
 <li class="toctree-l2"><a class="reference internal" href="configuration.html#static-media">Static Media</a></li>
 </ul>
 </li>
+<li class="toctree-l1"><a class="reference internal" href="usage.html">Using Django Admin Sortable</a><ul>
+<li class="toctree-l2"><a class="reference internal" href="usage.html#models">Models</a></li>
+</ul>
+</li>
 <li class="toctree-l1"><a class="reference internal" href="testing.html">Testing</a></li>
 </ul>