fix #245 on reconnect, update the connecting field with the current connection attempt Cancellable
fix #181 allow configuring reconnectDelay and reconnectDelayMax for socket.io
name threads created by AsyncServer.synchronousWorkers
auto-shrink AsyncServer.synchronousWorkers threadpool when idle
randomize socket.io reconnect delays +/-50% to avoid a thundering herd of synchronized clients reconnecting on the same schedule after a server-side outage