Fix demo to run as memory only

rails-app/demo.yml

@@ -2,6 +2,7 @@ version: '3.4'
 services:
   db:
     image: postgres
+    tmpfs: /var/lib/postgresql/data
 
   super_graph:
     image: dosco/super-graph:latest
@@ -16,6 +17,7 @@ services:
     image: dosco/super-graph-demo:latest
     environment:
       RAILS_ENV: "development"
+    tmpfs: /app/tmp/pids
     ports:
       - "3000:3000"
     depends_on: