Migrate from socket.io based RCStream to SSE / EventSource based EventStreams

Hiya! WMF plans to decomission the socket.io based RCStream in July this year. We've built a new service called EventStreams that takes its place.

- https://blog.wikimedia.org/2017/03/20/eventstreams/
- https://wikitech.wikimedia.org/wiki/EventStreams

Let us know if there is any way we can help with the switchover.

Thanks!