Options for client should optional

like the readme example

fixes #14

lib/client.js

@@ -94,6 +94,11 @@ function clientSession(sock, options) {
  * @param func callback(err, session)
  */
 function client(options, callback) {
+	if (typeof options === 'function') {
+		callback = options;
+		options  = {};
+	}
+	
 	var sock = new net.Socket();
 
 	// Set default options