Use require.js where possible.

IPython/html/static/notebook/js/widget.js

@@ -16,12 +16,11
  */
 
 
-// require(['components/underscore/underscore-min.js',
-//          'components/backbone/backbone-min.js'],
-
 "use strict";
 
 // Only run once on a notebook.
+require(["components/underscore/underscore-min", 
+         "components/backbone/backbone-min"], function () {
 if (IPython.notebook.widget_manager == undefined) {
 
     //-----------------------------------------------------------------------
@@ -255,3 +254,4 if (IPython.notebook.widget_manager == undefined) {
     IPython.notebook.widget_manager = new WidgetManager(IPython.notebook.kernel.comm_manager);    
 
 }
+});

IPython/html/templates/page.html

@@ -71,8 +71,6
 <script src="{{static_url("components/jquery/jquery.min.js") }}" type="text/javascript" charset="utf-8"></script>
 <script src="{{static_url("components/jquery-ui/ui/minified/jquery-ui.min.js") }}" type="text/javascript" charset="utf-8"></script>
 <script src="{{static_url("components/bootstrap/bootstrap/js/bootstrap.min.js") }}" type="text/javascript" charset="utf-8"></script>
-<script src="{{static_url("components/underscore/underscore-min.js") }}" type="text/javascript" charset="utf-8"></script>
-<script src="{{static_url("components/backbone/backbone-min.js") }}" type="text/javascript" charset="utf-8"></script>
 <script src="{{static_url("base/js/namespace.js") }}" type="text/javascript" charset="utf-8"></script>
 <script src="{{static_url("base/js/page.js") }}" type="text/javascript" charset="utf-8"></script>
 <script src="{{static_url("auth/js/loginwidget.js") }}" type="text/javascript" charset="utf-8"></script>