make it possible to use a regexp to match the socket.io resource URL

[fjakobs]

We need this because we have to prefix the socket.io URL with a variable
ID.

[fjakobs]

In Cloud9 we shard IDE workspaces based on the workspace id (e.g. fjakobs/ace) to different backend servers. Dispatching is done based on a URL prefix e.g. /fjakobs/ace/...

I want to attach the socket.io URL below these prefixes /fjakobs/ace/socket.io
With this patch I can easily do that with one socket.io instance by using a regexp as resource:

socketIo.listen(server, {
    resource: /^(?:\/[\w\d_\-]+){2}\/socket\.io/
})

[rauchg]

Oh sounds good!

[rauchg]

In the next major version I'll explain how to also pass requests without listen, in a way that you can capture with completely arbitrary rules. This is already possible in engine.io/websocket.io by calling handleRequest/handleUpgrade and passing the request/upgraded request objects.

However, having the regexp is definitely handly. Thanks!

[fjakobs]

being able to pass requests without listen would be really handy. Thanks for the pull.