Fixup connection refused errors (#656)

When starting the development setup through docker-compose, the logs
would display an ERRCONNREFUSED but this doesn't seem to have any effect
on development. However changing the proxy to point to the internal
backend service name from the docker network seems to fix these and
continues to let things work as expected

Author: Tonkpils

docker-compose.yml

@@ -49,7 +49,7 @@ services:
       - 4300:4300
     volumes:
       - ./frontend:/app
-    command: sh -c "cd /app && rm -rfd ./dist && ./node_modules/.bin/ember serve --port 4300 --proxy http://localhost:3000"
+    command: sh -c "cd /app && rm -rfd ./dist && ./node_modules/.bin/ember serve --port 4300 --proxy http://backend:3000"
     profiles:
       - dev
   app-setup: