Clean up handling of es6 promise

jupyterlab/package.json

@@ -35,7 +35,7 @@
     "@jupyterlab/shortcuts-extension": "^0.1.1",
     "@jupyterlab/terminal-extension": "^0.1.1",
     "@jupyterlab/tooltip-extension": "^0.1.1",
-    "es6-promise": "^3.1.2",
+    "es6-promise": "^4.0.5",
     "font-awesome": "^4.6.3"
   },
   "devDependencies": {

jupyterlab/src/main.ts

@@ -1,9 +1,7 @@
 // Copyright (c) Jupyter Development Team.
 // Distributed under the terms of the Modified BSD License.
 
-import {
-  polyfill
-}  from 'es6-promise';
+import 'es6-promise/auto';  // polyfill Promise on IE
 
 import {
   JupyterLab, ModuleLoader
@@ -88,9 +86,6 @@ import 'font-awesome/css/font-awesome.min.css';
 import '@jupyterlab/default-theme/style/index.css';
 
 
-polyfill();
-
-
 /* tslint:disable */
 const mods: JupyterLab.IPluginModule[] = [
 aboutExtension,