Tyranid client subscriptions use polling instead of websockets

[yangchristian]

If you look at network traffic, client subscriptions use polling:

I think we may want to change the socket.io server setup call to use listen() instead based on the following stack overflow threads:

• https://stackoverflow.com/a/24186912/1406819
• https://stackoverflow.com/a/17697134/1406819 (referenced by first answer)

We might also need to make sure the client transport option is set to use sockets: https://stackoverflow.com/a/41396396/1406819 (although it seems odd that it'd default to polling)

Looks like even though the option prioritizes polling, there is a default behavior to upgrade to sockets: socketio/socket.io-client#883