example guestbook broken

the manifests use gcr.io/google-samples/gb-frontend:v4 for frontend. 
gcr.io/google-samples/gb-frontend:v4 has been replaced with v5

but v5 doesn't work. 

php-redis is not installed so the front end php code is unable to communicate with redis. 

there may be more issues. That is as far as I got before abandoning working with the example. 

