Allow the use of a custom parser

See socketio/socket.io#2829

Author: Damien Arrachequesne

lib/manager.js

@@ -62,8 +62,9 @@ function Manager (uri, opts) {
   this.lastPing = null;
   this.encoding = false;
   this.packetBuffer = [];
-  this.encoder = new parser.Encoder();
-  this.decoder = new parser.Decoder();
+  var _parser = opts.parser || parser;
+  this.encoder = new _parser.Encoder();
+  this.decoder = new _parser.Decoder();
   this.autoConnect = opts.autoConnect !== false;
   if (this.autoConnect) this.open();
 }