refactor docker compose file

Author: James Lee

common.yml

@@ -0,0 +1,7 @@
+version: '2'
+services:
+  dockerapp:
+    ports:
+      - "5000:5000"
+  redis:
+    image: redis:3.2.0

docker-compose.yml

@@ -1,9 +1,12 @@
 version: '2'
 services:
   dockerapp:
+    extends:
+      file: common.yml
+      service: dockerapp
     build: .
-    ports:
-      - "5000:5000"
 
   redis:
-    image: redis:3.2.0
+    extends:
+      file: common.yml
+      service: redis

prod.yml

@@ -1,9 +1,12 @@
 version: '2'
 services:
   dockerapp:
+    extends:
+      file: common.yml
+      service: dockerapp
     image: jleetutorial/dockerapp
-    ports:
-      - "5000:5000"
 
   redis:
-    image: redis:3.2.0
+    extends:
+      file: common.yml
+      service: redis