changed the 'we need help' link to the new help page

index.html

@@ -128,7 +128,7 @@
     We're looking for people to help maintain and improve vis.js.
     <br/>
     <br/>
-    Interested? <a href="https://github.com/almende/vis/issues/1781" target="_blank">Click here</a>
+    Interested? <a href="https://github.com/almende/vis/blob/develop/misc/we_need_help.md" target="_blank">Click here</a>
 </div>
 
 <!-- Marketing messaging and featurettes
@@ -347,4 +347,3 @@
 <script src="./js/bootstrap.min.js"></script>
 <!-- IE10 viewport hack for Surface/desktop Windows 8 bug -->
 <script src="./js/ie10-viewport-bug-workaround.js"></script>
-