Speed up build (#1852)

* single build webpack

* fix demo shell test

demo-shell-ng2/config/helpers.js

@@ -1,7 +1,10 @@
 var path = require('path');
+
 var _root = path.resolve(__dirname, '..');
+
 function root(args) {
   args = Array.prototype.slice.call(arguments, 0);
   return path.join.apply(path, [_root].concat(args));
 }
+
 exports.root = root;