Using WebSockets within an app doesn't work

[tiff]

The heroku websockets example isn't working: https://devcenter.heroku.com/articles/node-websockets

It seems that the Upgrade: websocket header is never reaching the app because we are removing it in central-gateway proxy.

See;
https://golang.org/src/net/http/httputil/reverseproxy.go#L90
https://github.com/experimental-platform/platform-central-gateway/blob/development/server.go#L37