Added database location to .env because of issue with OS X

.env

@@ -13,3 +13,4 @@ BACKEND_PORT=5001
 FRONTEND_PORT=3001
 FRONTEND_PORT_HTTPS=3443
 OUTER_HOSTNAME=shuffle-backend
+DB_LOCATION=/etc/shuffle

docker-compose.yml

@@ -24,7 +24,7 @@ services:
       - shuffle
     restart: unless-stopped
     volumes:
-      - /etc/shuffle:/etc/shuffle
+      - ${DB_LOCATION}:/etc/shuffle
   backend:
     #build: ./backend
     image: frikky/shuffle:backend