Update collection docs on underscore methods.

index.html

@@ -362,7 +362,7 @@
       <li>– <a href="#Collection-models">models</a></li>
       <li>– <a href="#Collection-toJSON">toJSON</a></li>
       <li>– <a href="#Collection-sync">sync</a></li>
-      <li>– <a href="#Collection-Underscore-Methods"><b>Underscore Methods (28)</b></a></li>
+      <li>– <a href="#Collection-Underscore-Methods"><b>Underscore Methods (32)</b></a></li>
       <li>– <a href="#Collection-add">add</a></li>
       <li>– <a href="#Collection-remove">remove</a></li>
       <li>– <a href="#Collection-reset">reset</a></li>
@@ -1682,9 +1682,9 @@ <h2 id="Collection">Backbone.Collection</h2>
     </p>
 
     <p id="Collection-Underscore-Methods">
-      <b class="header">Underscore Methods (28)</b>
+      <b class="header">Underscore Methods (32)</b>
       <br />
-      Backbone proxies to <b>Underscore.js</b> to provide 28 iteration functions
+      Backbone proxies to <b>Underscore.js</b> to provide 32 iteration functions
       on <b>Backbone.Collection</b>. They aren't all documented here, but
       you can take a look at the Underscore documentation for the full details&hellip;
     </p>
@@ -1710,13 +1710,18 @@ <h2 id="Collection">Backbone.Collection</h2>
       <li><a href="http://underscorejs.org/#size">size</a></li>
       <li><a href="http://underscorejs.org/#first">first (head, take)</a></li>
       <li><a href="http://underscorejs.org/#initial">initial</a></li>
-      <li><a href="http://underscorejs.org/#rest">rest (tail)</a></li>
+      <li><a href="http://underscorejs.org/#rest">rest (tail, drop)</a></li>
       <li><a href="http://underscorejs.org/#last">last</a></li>
       <li><a href="http://underscorejs.org/#without">without</a></li>
       <li><a href="http://underscorejs.org/#indexOf">indexOf</a></li>
       <li><a href="http://underscorejs.org/#lastIndexOf">lastIndexOf</a></li>
       <li><a href="http://underscorejs.org/#isEmpty">isEmpty</a></li>
       <li><a href="http://underscorejs.org/#chain">chain</a></li>
+      <li><a href="http://underscorejs.org/#difference">difference</a></li>
+      <li><a href="http://underscorejs.org/#sample">sample</a></li>
+      <li><a href="http://underscorejs.org/#partition">partition</a></li>
+      <li><a href="http://underscorejs.org/#countBy">countBy</a></li>
+      <li><a href="http://underscorejs.org/#indexBy">indexBy</a></li>
     </ul>
 
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