The gateway doesn't serve anything on it's base address

[awheeler294]

Summary

When you run the gateway, the CLI output gateway serving on 127.0.0.1:PORT, but if you navigate there you just get a 404. We should serve something.

Steps to reproduce

1. Start the gateway
2. In a browser, navigate to the address it shows in the command line

Expected

Gateway should serve something up at that address, either an index.html or a redirect to /config

Notes

If /config is the only page currently, or is what we want as the default page, then the easiest thing would be a redirect, if we add more interaction to the gateway in the future then we can add an index.html