Merge remote-tracking branch 'pull/991'

* pull/991:
  External Links: Added Umali book on Git

Author: peff

app/views/doc/ext.html.erb

@@ -171,6 +171,13 @@
             By Aske Olsson and Rasmus Voss
           </p>
         </li>
+	 <li>
+	  <a href="https://www.manning.com/books/learn-git-in-a-month-of-lunches"><img src="https://www.manning.com/umali/umali_cover150.jpg" width="107"></a>
+	  <h4><a href="https://www.manning.com/books/learn-git-in-a-month-of-lunches">Learn Git in a Month of Lunches</a></h4>
+	  <p class='description'>
+	    By Rick Umali
+	  </p>
+	 </li>
       </ul>
     </div>
   </div>