Revise user-guide to use separate package for proto code

[meling]

trafficstars

We mention this in the user-guide.md file: Note: For a real use case, you may decide to keep the .proto file, and the generated .pb.go files in a separate directory/package and import that package (the generated Gorums API) into your application.

We should rework the user-guide to follow this practice instead and delete this comment.