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() {

node_zeromq/zmq.d.ts

@@ -3,6 +3,8 @@
 // Definitions by: Dave McKeown <http://github.com/davemckeown>
 // Definitions: https://github.com/borisyankov/DefinitelyTyped
 
+/// <reference path='../node/node-0.11.d.ts' />
+
 interface EventEmitter {}
 
 declare module 'zmq' {
@@ -150,6 +152,13 @@ declare module 'zmq' {
          */
         close(): Socket;
 
+        /**
+         * Socket event
+         * @param eventName {string}
+         * @param callback {Function}
+         */
+        on(eventName: string, callback: (buffer: Buffer) => void): void;
+
         // Socket Options
         _fd: any;
         _ioevents: any;