Add tooling to set content handling in integration response automatically

Manually having to set Content Handling = "Convert to binary (if needed)" after each deploy is a nuisance, especially since the only way to test things out is to deploy the new version. This [can be set with
`boto3`](http://boto3.readthedocs.io/en/latest/reference/services/apigateway.html#APIGateway.Client.update_integration_response) but some thought needs to go into how to make it work.

The issue points to boto3's APIGateway.Client.update_integration_response; start there and trace how the project's deployment tooling configures API Gateway integration responses. Done means deployments automatically apply Content Handling = "Convert to binary (if needed)" without manual intervention, with a repeatable way to verify it.

Written by the indexing model from the issue text.