Fix possible race condition when attaching clients

[xPaw]

Socket events were bound before attaching client, so technically an event could be trigger before there is an attached client and crash. I believe this fixes the issue.

        this.attachedClients[socketId].openChannel = target.chan.id;
                                                   ^
 
TypeError: Cannot set property 'openChannel' of undefined
    at Client.open (/home/irc/root/lounge/src/client.js:438:45)
    at Socket.<anonymous> (/home/irc/root/lounge/src/server.js:318:11)
    at emitOne (events.js:115:13)
    at Socket.emit (events.js:210:7)
    at /home/irc/root/lounge/node_modules/socket.io/lib/socket.js:503:12
    at _combinedTickCallback (internal/process/next_tick.js:131:7)
    at process._tickCallback (internal/process/next_tick.js:180:9)