update oauth2 example

see google's schedule for service shutdown date (sept 1, 2014 sunset) on these two scopes: userinfo.profile & userinfo.email, https://developers.google.com/+/api/auth-migration#timetable

examples/oauth2/app.js

@@ -88,8 +88,7 @@ app.get('/login', function(req, res){
 //   redirecting the user to google.com.  After authorization, Google
 //   will redirect the user back to this application at /auth/google/callback
 app.get('/auth/google',
-  passport.authenticate('google', { scope: ['https://www.googleapis.com/auth/userinfo.profile',
-                                            'https://www.googleapis.com/auth/userinfo.email'] }),
+  passport.authenticate('google', { scope: ['https://www.googleapis.com/auth/plus.login'] }),
   function(req, res){
     // The request will be redirected to Google for authentication, so this
     // function will not be called.