Added cors to postgraphile

Necessary for all apollo clients to work properly.
However, this is not optimal since preflight caching is not working properly.
This will be addressed in issue #15

docker-compose.dev.yml

@@ -51,6 +51,7 @@ services:
       "--connection", $DATABASE_URL,
       "--host", "0.0.0.0",
       "--port", "5000",
+      "--cors",
       "--schema", "candymat_data",
       "--default-role", "candymat_anonymous",
       "--jwt-token-identifier", "candymat_data.jwt_token",