stream: function() support doesn't work as documented.

The docs say that the function is async and should call a callback upon creation of the stream.

  stream: function (cb) {
    const newStream = new SocksConnection({host: 'remote.host', port: 3306}, {host: 'localhost', port: 1080});
    cb(null, newStream);
  }

The code says the function is synchronous and should return the stream.

      // if stream is a function, treat it as "stream agent / factory"
      if (typeof opts.config.stream == 'function') {
        this.stream = opts.config.stream(opts);
      } else {

Compare the documented stream option with the implementation around the shown opts.config.stream branch. Determine whether the stream factory should use a callback or return a stream, then align the implementation and documentation so the stated contract is consistent and verifiable.