Add Networks!

Signed-off-by: Dave Tucker <dave@dtucker.co.uk>

docker-compose.yml

@@ -1,36 +1,56 @@
 version: "2"
+
 services:
   voting-app:
     build: ./voting-app/.
     volumes:
-      - ./voting-app:/app
+     - ./voting-app:/app
     ports:
       - "5000:80"
     links:
       - redis
+    networks:
+      - front-tier
+      - back-tier
 
-  redis:
-    image: redis
-    ports: ["6379"]
+  result-app:
+    build: ./result-app/.
+    volumes:
+      - ./result-app:/app
+    ports:
+      - "5001:80"
+    links:
+      - db
+    networks:
+      - front-tier
+      - back-tier
 
   worker:
     build: ./worker
     links:
       - db
       - redis
+    networks:
+      - back-tier
+
+  redis:
+    image: redis
+    ports: ["6379"]
+    networks:
+      - back-tier
 
   db:
     image: postgres:9.4
     volumes:
-      - "myvolume:/var/lib/postgresql/data"
+      - "db-data:/var/lib/postgresql/data"
+    networks:
+      - back-tier
 
-  result-app:
-    build: ./result-app/.
-    volumes:
-      - ./result-app:/app
-    ports:
-      - "5001:80"
-    links:
-      - db
 volumes:
-  myvolume:
+  db-data:
+
+networks:
+  front-tier:
+  back-tier:
+
+