add docker compose for pg

.gitignore

@@ -2,3 +2,4 @@
 **/c.html
 bookings
 database.yml
+postgres/docker-compose.yml

postgres/docker-compose-example.yml

@@ -0,0 +1,25 @@
+# Use postgres/postgres user/password credentials
+services:
+
+  db:
+    image: postgres
+    restart: always
+    # set shared memory limit when using docker-compose
+    shm_size: 128mb
+    # or set shared memory limit when deploy via swarm stack
+    #volumes:
+    #  - type: tmpfs
+    #    target: /dev/shm
+    #    tmpfs:
+    #      size: 134217728 # 128*2^20 bytes = 128Mb
+    environment:
+      POSTGRES_PASSWORD: postgres
+    ports:
+      - 5432:5432
+
+  adminer:
+    image: adminer
+    restart: always
+    ports:
+      - 8081:8080
+