Alternate endpoint support.

I understand that this is targeted at lambda, which is stateless.
We have a need to keep a large model in memory, ~1GB deserialized from s3, so doing so for each API call is not practical so lambda is not an option, but the rest of the framework is ideal.

Coupling the API GW front-end to an ec2 instance backed endpoint, rather than a lambda service, incurs a large amount of additional wiring for what is a variation on the back-end implementation, ie: lambda vs an http endpoint.

This framework would be very useful for non-lambda services tied to the API GW as well.