Add .on() function to zeromq and a test for it.

node_zeromq/zmq-tests.ts

@@ -1,4 +1,5 @@
 /// <reference path='zmq.d.ts' />
+/// <reference path='../node/node-0.11.d.ts' />
 
 import zmq = require('zmq');
 
@@ -18,6 +19,9 @@ function test3() {
     var sock = zmq.socket('push');
     sock.bindSync('tcp://127.0.0.1:3000');
     sock.send(['hello', 'world']);
+    sock.on('message', function (buffer: Buffer) {
+        //
+    });
 }
 
 function test4() {