Using both produces and response

[denisovkv]

Closes #187

[artcg]

Nice job, looks like you can also remove the block of code

if len(route_spec.response) == 0:
                responses["200"] = {
                    "schema": serialize_schema(route_spec.produces.field) if route_spec.produces else None,
                    "description": route_spec.produces.description if route_spec.produces else None,
                }

As the code you wrote replaces that

[denisovkv]

@artcg forgot to push, thank you :)

[ahopkins]

@denisovkv Can you take a look at this conflict?

[denisovkv]

@ahopkins Done