Updated dataAttributes documentation for 'all' option

docs/timeline.html

@@ -381,9 +381,10 @@ var options = {
 
 <tr>
   <td>dataAttributes</td>
-  <td>Array[String]</td>
+  <td>Array[String] | 'all'</td>
   <td>false</td>
-  <td>An array of fields optionally defined on the timeline items that will be appended as <code>data-</code> attributes to the DOM element of the items.</td>
+  <td>An array of fields optionally defined on the timeline items that will be appended as <code>data-</code> attributes to the DOM element of the items.<br>
+    If value is <code>'all'</code> then each field defined on the timeline item will become a <code>data-</code> attribute.</td>
 </tr>