changed ESC to trigger collapsing of the pager in notebook

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

@@ -130,6 +130,7 b' var IPython = (function (IPython) {'
             } else if (event.which === key.ESC) {
                 // Intercept escape at highest level to avoid closing
                 // websocket connection with firefox
+                that.element.trigger('collapse_pager');
                 event.preventDefault();
             } else if (event.which === key.SHIFT) {
                 // ignore shift keydown