fix: use the correct link for slideshare presentations

Author: etorreborre

guide/src/test/resources/learn.html

@@ -39,7 +39,7 @@
       </li>
       <li><s2>specs2</s2> presentations on Slideshare
       </li>
-      <iframe src="https://www.slideshare.net/specs2/slideshelf" width="615px" height="470px" frameborder="0" marginwidth="0" marginheight="0" scrolling="no" style="border:none;" ></iframe>
+      <iframe src="https://www.slideshare.net/specs2/presentations" width="615px" height="470px" frameborder="0" marginwidth="0" marginheight="0" scrolling="no" style="border:none;" ></iframe>
 
   </ul>
 </div>

guide/src/test/resources/nav.html

@@ -39,7 +39,7 @@
                         <li><a href="http://github.com/etorreborre/specs2">Github</a></li>
                         <li><a href="http://github.com/etorreborre/specs2/issues">Issues</a></li>
                         <li><a href="http://stackoverflow.com/questions/tagged/specs2">Questions</a></li>
-                        <li><a href="http://www.slideshare.net/specs2">Presentations</a></li>
+                        <li><a href="http://www.slideshare.net/specs2/presentations">Presentations</a></li>
                     </ul>
                 </li>
             </ul>

guide/src/test/resources/project.html

@@ -35,7 +35,7 @@
       </div>
 
       <div class="col-md-3 panel">
-        <a href="http://www.slideshare.net/specs2"><img src="$SITE_DIR$/images/slideshare.jpeg"/></a>
+        <a href="http://www.slideshare.net/specs2/presentations"><img src="$SITE_DIR$/images/slideshare.jpeg"/></a>
       </div>
     </div>
     <div class="row">
@@ -52,7 +52,7 @@
         </div>
 
         <div class="col-md-3 panel">
-            <a href="http://www.slideshare.net/specs2">Presentations</a>
+            <a href="http://www.slideshare.net/specs2/presentations">Presentations</a>
         </div>