This removes the warnings produced by the invalid callout in the boot
reference. It also provides an example of how to customize the redis
connection and links to the "Connection to Redis" section of the
Spring Boot reference.
Issue #108
Previously there was a possibility that Session to WebSocket mapping was
leaked if keyspace notifications were not enabled in Redis.
To resolve this the RedisHttpSessionConfiguration now ensures that Redis
is configured to enable Keyspace notifications.
Fixes gh-76 gh-81
