After deploying the server to Zeit unable to perform first query from the tutorial.

After setting up the client and writing first query from part 5 of the tutorial, query isn't performed against deployed service:
```
Cross-Origin Request Blocked: The Same Origin Policy disallows reading the remote resource at https://server-ik661tevx.now.sh/graphql. (Reason: CORS preflight channel did not succeed)
```

Start with part 5 of the tutorial and reproduce the first query against the deployed GraphQL endpoint. Inspect the failed CORS preflight request and the server's deployment configuration; done means the tutorial client can perform its first query against the deployed service.

Written by the indexing model from the issue text.