fix use assign module instead of Object.assign

Object.assign not available in most browser yet...

common/app/app-stream.jsx

@@ -1,4 +1,5 @@
 import Rx from 'rx';
+import assign from 'object.assign';
 import { Router } from 'react-router';
 import App from './App.jsx';
 
@@ -6,7 +7,7 @@ import childRoutes from './routes';
 
 const router$ = Rx.Observable.fromNodeCallback(Router.run, Router);
 
-const routes = Object.assign({ components: App }, childRoutes);
+const routes = assign({ components: App }, childRoutes);
 
 export default function app$(location) {
   return router$(routes, location);