Implement example: functions_memorystore_redis

[coryan]

Need to verify we have the pre-requisites to connect to a redis instance (possibly using hiredis). Then use:

https://github.com/GoogleCloudPlatform/golang-samples/blob/master/functions/memorystore/redis/visitcount.go#L15-L85

https://github.com/GoogleCloudPlatform/python-docs-samples/blob/master/functions/memorystore/redis/main.py#L15-L30

[coryan]

This can be done post-GA, several languages do not have this example.