Expose postgres ports

Remove linking, which was deprecated.
This fixes the issue where the db does not start.

docker-compose.yml

@@ -3,6 +3,10 @@ version: '2.1'
 services:
   db:
     image: postgres:9.4
+    ports:
+      - "5432:5432"
+    environment:
+      - POSTGRES_HOST_AUTH_METHOD=trust
 
   web:
     build:
@@ -12,8 +16,6 @@ services:
       - "5000:5000"
     depends_on:
       - db
-    links:
-      - db
     command: serve
     volumes:
       - ./:/app/