fix dialog polyfill usage

demo-shell-ng2/app/vendor.ts

@@ -38,7 +38,7 @@ import 'material-design-icons/iconfont/material-icons.css';
 import 'flag-icon-css/css/flag-icon.min.css';
 
 // Polyfill(s) for dialogs
-import 'dialog-polyfill/dialog-polyfill';
+require('script!dialog-polyfill/dialog-polyfill');
 import 'dialog-polyfill/dialog-polyfill.css';
 
 // app content

demo-shell-ng2/config/webpack.common.js

@@ -106,10 +106,6 @@ module.exports = {
 
     plugins: [
 
-        new webpack.ProvidePlugin({
-            'dialogPolyfill': 'dialog-polyfill/dialog-polyfill'
-        }),
-
         new CopyWebpackPlugin([
             { from: 'versions.json' }
         ]),