readyState bug while sending data from server

[itsfuad]

Current implementation of socketio doesn't have if (this.writable && this.readyState === "open") check before sending the data. This causes server crash.

Because the code was on the Render cloud, I did not found any way to reproduce it on my pc. Thus by adding this.readyState === "open" check, the issue was fixed.

I pulled a request with the fix.

[darrachequesne]

This should be fixed by d08f8f2, included in release 0.2.1.

Thanks!