Modified response.

Now query parameter 'name' is used to send the greeting back. Yet, the query parameter is not validated.
Try, http://localhost:8000/hello?name=Sam
Validation performed.

- Validation is performed to make sure that the query parameter 'name' exists and it is indeed of type string.
- Try http://localhost:8000/hello as opposed to http://localhost:8000/hello?name=Sam