Add a command-line interface to rb-gateway

Review Request #10015 — Created June 11, 2018 and submitted — Latest diff uploaded

Information

rb-gateway
master
94e5e36...

Reviewers

We now bring in kingpin for argument parsing. This allows us to
specify the path to the configuration file.

Ran go fmt ./....
Ran go test ./....
Ran rb-gateway --config with a different config file.