added events module (from nodejs)

+// Copyright Joyent, Inc. and other Node contributors.
+//
+// Permission is hereby granted, free of charge, to any person obtaining a
+// copy of this software and associated documentation files (the
+// "Software"), to deal in the Software without restriction, including
+// without limitation the rights to use, copy, modify, merge, publish,
+// distribute, sublicense, and/or sell copies of the Software, and to permit
+// persons to whom the Software is furnished to do so, subject to the
+// following conditions:
+//
+// The above copyright notice and this permission notice shall be included
+// in all copies or substantial portions of the Software.
+//
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
+// OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+// MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN
+// NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM,
+// DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR
+// OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE
+// USE OR OTHER DEALINGS IN THE SOFTWARE.
+
+var isArray = Array.isArray;
+
+function EventEmitter() { }
+exports.EventEmitter = EventEmitter;
+
+// By default EventEmitters will print a warning if more than
+// 10 listeners are added to it. This is a useful default which
+// helps finding memory leaks.
+//
+// Obviously not all Emitters should be limited to 10. This function allows
+// that to be increased. Set to zero for unlimited.
+var defaultMaxListeners = 10;
+EventEmitter.prototype.setMaxListeners = function(n) {
+  if (!this._events) this._events = {};
+  this._maxListeners = n;
+};
+
+
+EventEmitter.prototype.emit = function() {
+  var type = arguments[0];
+  // If there is no 'error' event listener then throw.
+  if (type === 'error') {
+    if (!this._events || !this._events.error ||
+        (isArray(this._events.error) && !this._events.error.length))
+    {
+      if (arguments[1] instanceof Error) {
+        throw arguments[1]; // Unhandled 'error' event
+      } else {
+        throw new Error("Uncaught, unspecified 'error' event.");
+      }
+      return false;
+    }
+  }
+
+  if (!this._events) return false;
+  var handler = this._events[type];
+  if (!handler) return false;
+
+  if (typeof handler == 'function') {
+    switch (arguments.length) {
+      // fast cases
+      case 1:
+        handler.call(this);
+        break;
+      case 2:
+        handler.call(this, arguments[1]);
+        break;
+      case 3:
+        handler.call(this, arguments[1], arguments[2]);
+        break;
+      // slower
+      default:
+        var l = arguments.length;
+        var args = new Array(l - 1);
+        for (var i = 1; i < l; i++) args[i - 1] = arguments[i];
+        handler.apply(this, args);
+    }
+    return true;
+
+  } else if (isArray(handler)) {
+    var l = arguments.length;
+    var args = new Array(l - 1);
+    for (var i = 1; i < l; i++) args[i - 1] = arguments[i];
+
+    var listeners = handler.slice();
+    for (var i = 0, l = listeners.length; i < l; i++) {
+      listeners[i].apply(this, args);
+    }
+    return true;
+
+  } else {
+    return false;
+  }
+};
+
+// EventEmitter is defined in src/node_events.cc
+// EventEmitter.prototype.emit() is also defined there.
+EventEmitter.prototype.addListener = function(type, listener) {
+  if ('function' !== typeof listener) {
+    throw new Error('addListener only takes instances of Function');
+  }
+
+  if (!this._events) this._events = {};
+
+  // To avoid recursion in the case that type == "newListeners"! Before
+  // adding it to the listeners, first emit "newListeners".
+  this.emit('newListener', type, listener);
+
+  if (!this._events[type]) {
+    // Optimize the case of one listener. Don't need the extra array object.
+    this._events[type] = listener;
+  } else if (isArray(this._events[type])) {
+
+    // If we've already got an array, just append.
+    this._events[type].push(listener);
+
+    // Check for listener leak
+    if (!this._events[type].warned) {
+      var m;
+      if (this._maxListeners !== undefined) {
+        m = this._maxListeners;
+      } else {
+        m = defaultMaxListeners;
+      }
+
+      if (m && m > 0 && this._events[type].length > m) {
+        this._events[type].warned = true;
+        console.error('(node) warning: possible EventEmitter memory ' +
+                      'leak detected. %d listeners added. ' +
+                      'Use emitter.setMaxListeners() to increase limit.',
+                      this._events[type].length);
+        console.trace();
+      }
+    }
+  } else {
+    // Adding the second element, need to change to array.
+    this._events[type] = [this._events[type], listener];
+  }
+
+  return this;
+};
+
+EventEmitter.prototype.on = EventEmitter.prototype.addListener;
+
+EventEmitter.prototype.once = function(type, listener) {
+  if ('function' !== typeof listener) {
+    throw new Error('.once only takes instances of Function');
+  }
+
+  var self = this;
+  function g() {
+    self.removeListener(type, g);
+    listener.apply(this, arguments);
+  };
+
+  g.listener = listener;
+  self.on(type, g);
+
+  return this;
+};
+
+EventEmitter.prototype.removeListener = function(type, listener) {
+  if ('function' !== typeof listener) {
+    throw new Error('removeListener only takes instances of Function');
+  }
+
+  // does not use listeners(), so no side effect of creating _events[type]
+  if (!this._events || !this._events[type]) return this;
+
+  var list = this._events[type];
+
+  if (isArray(list)) {
+    var position = -1;
+    for (var i = 0, length = list.length; i < length; i++) {
+      if (list[i] === listener ||
+          (list[i].listener && list[i].listener === listener))
+      {
+        position = i;
+        break;
+      }
+    }
+
+    if (position < 0) return this;
+    list.splice(position, 1);
+    if (list.length == 0)
+      delete this._events[type];
+  } else if (list === listener ||
+             (list.listener && list.listener === listener))
+  {
+    delete this._events[type];
+  }
+
+  return this;
+};
+
+EventEmitter.prototype.removeAllListeners = function(type) {
+  if (arguments.length === 0) {
+    this._events = {};
+    return this;
+  }
+
+  // does not use listeners(), so no side effect of creating _events[type]
+  if (type && this._events && this._events[type]) this._events[type] = null;
+  return this;
+};
+
+EventEmitter.prototype.listeners = function(type) {
+  if (!this._events) this._events = {};
+  if (!this._events[type]) this._events[type] = [];
+  if (!isArray(this._events[type])) {
+    this._events[type] = [this._events[type]];
+  }
+  return this._events[type];
+};