Update to support Socket.io 2.x?

[TomiS]

This library seems valuable but the bindings seem to be outdated a bit. Socket.io released 2.0 in 2017 and it seems to be now well stabilized at version 2.3. I've understood the differences to 1.x should be quite minimal.

I realize making a PR would be the thing to do but for now I have to settle for making this ticket.

Here's 2.0.0 release notes (only 2 breaking changes, it seems)
https://github.com/socketio/socket.io/releases/tag/2.0.0

Here's the latest (currently 2.3.0) API documentation for reference:
https://github.com/socketio/socket.io/blob/2.3.0/docs/API.md