Add Swagger Support to API

Opening this for tracking. I don't yet have a proposed solution or data architecture yet.

When I've used the grpc-gateway project in the past, on of my favorite features was the auto-swagger generator. With strongly-typed requests and responses coming from Protocol Buffers, the gateway had all the information it needed to generate the API definition.

I think that an auto-documentation tool built into Buffalo would make it more developer friendly.

The most radical way we could do this would be to use grpc-gateway, use protocol buffers to generate the API definitions, and simultaneously support gRPC with REST. However, I think this seems heavy-handed.

@markbates Do you have any thoughts or opinions on this?