Add node references (#1123)

Removes old Kubernetes references to master / slave and converts them to
master / node.

examples/docker-compose-v3.yaml

@@ -7,7 +7,7 @@ services:
     ports:
       - "6379"
 
-  redis-slave:
+  redis-node:
     image: gcr.io/google_samples/gb-redisslave:v1
     ports:
       - "6379"

examples/docker-compose.yaml

@@ -7,7 +7,7 @@ services:
     ports:
       - "6379"
 
-  redis-slave:
+  redis-node:
     image: gcr.io/google_samples/gb-redisslave:v1
     ports:
       - "6379"