Add shadow to pager handle

IPython/html/static/notebook/less/pager.less

@@ -49,6 +49,11 b' div#pager {'
         border-top: 1px solid @light_border_color;
         border-bottom: 1px solid @light_border_color;
 
+        /* Similar to the notebook header's shadow, but not
+        exactly the same.  The settings had to be adjusted
+        to get the shadow to show. */
+        .box-shadow(1px 4px 9px -4px rgba(0, 0, 0, 0.25));
+
         /* This injects handle bars (a short, wide = symbol) for 
         the resize handle. */
         &::after {