use bootstrap `disabled` instead of `ui-state-disabled`

in menubar

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

@@ -724,7 +724,7 b' var IPython = (function (IPython) {'
         var i = this.index_or_selected(index);
         var cell = this.get_selected_cell();
         this.undelete_backup = cell.toJSON();
-        $('#undelete_cell').removeClass('ui-state-disabled');
+        $('#undelete_cell').removeClass('disabled');
         if (this.is_valid_cell_index(i)) {
             var ce = this.get_cell_element(i);
             ce.remove();
@@ -1005,11 +1005,11 b' var IPython = (function (IPython) {'
     Notebook.prototype.enable_paste = function () {
         var that = this;
         if (!this.paste_enabled) {
-            $('#paste_cell_replace').removeClass('ui-state-disabled')
+            $('#paste_cell_replace').removeClass('disabled')
                 .on('click', function () {that.paste_cell_replace();});
-            $('#paste_cell_above').removeClass('ui-state-disabled')
+            $('#paste_cell_above').removeClass('disabled')
                 .on('click', function () {that.paste_cell_above();});
-            $('#paste_cell_below').removeClass('ui-state-disabled')
+            $('#paste_cell_below').removeClass('disabled')
                 .on('click', function () {that.paste_cell_below();});
             this.paste_enabled = true;
         };
@@ -1022,9 +1022,9 b' var IPython = (function (IPython) {'
      */
     Notebook.prototype.disable_paste = function () {
         if (this.paste_enabled) {
-            $('#paste_cell_replace').addClass('ui-state-disabled').off('click');
-            $('#paste_cell_above').addClass('ui-state-disabled').off('click');
-            $('#paste_cell_below').addClass('ui-state-disabled').off('click');
+            $('#paste_cell_replace').addClass('disabled').off('click');
+            $('#paste_cell_above').addClass('disabled').off('click');
+            $('#paste_cell_below').addClass('disabled').off('click');
             this.paste_enabled = false;
         };
     };
@@ -1123,7 +1123,7 b' var IPython = (function (IPython) {'
             this.undelete_backup = null;
             this.undelete_index = null;
         }
-        $('#undelete_cell').addClass('ui-state-disabled');
+        $('#undelete_cell').addClass('disabled');
     }
 
     // Split/merge

IPython/html/templates/notebook.html

@@ -86,11 +86,11 b' class="notebook_app"'
             <ul class="dropdown-menu">
                 <li id="cut_cell"><a href="#">Cut Cell</a></li>
                 <li id="copy_cell"><a href="#">Copy Cell</a></li>
-                <li id="paste_cell_above" class="ui-state-disabled"><a href="#">Paste Cell Above</a></li>
-                <li id="paste_cell_below" class="ui-state-disabled"><a href="#">Paste Cell Below</a></li>
-                <li id="paste_cell_replace" class="ui-state-disabled"><a href="#">Paste Cell &amp; Replace</a></li>
+                <li id="paste_cell_above" class="disabled"><a href="#">Paste Cell Above</a></li>
+                <li id="paste_cell_below" class="disabled"><a href="#">Paste Cell Below</a></li>
+                <li id="paste_cell_replace" class="disabled"><a href="#">Paste Cell &amp; Replace</a></li>
                 <li id="delete_cell"><a href="#">Delete Cell</a></li>
-                <li id="undelete_cell" class="ui-state-disabled"><a href="#">Undo Delete Cell</a></li>
+                <li id="undelete_cell" class="disabled"><a href="#">Undo Delete Cell</a></li>
                 <li class="divider"></li>
                 <li id="split_cell"><a href="#">Split Cell</a></li>
                 <li id="merge_cell_above"><a href="#">Merge Cell Above</a></li>