Update socket.js

If "sync disconnect on unload" is set to true I was getting a lot of errors like these: 
 -> "XMLHttpRequest cannot load http://s1.test.com/socket.io/1//L1VtwrMiikmwXVoEQF2o/?disconnect=1. Origin http://www.teste2.com is not allowed by Access-Control-Allow-Origin."

I found out that this was being caused by the extra slash right before the session_id on the url! 

This fix removes that extra space on the uri formation (Why is it there?)

Best Regards