lib,src: remove usage of events.EventEmitter

The `events` module already exports `EventEmitter` constructor function
So, we don't have to use `events.EventEmitter` to access it.

Refer: https://github.com/nodejs/node/pull/2896

PR-URL: https://github.com/nodejs/node/pull/2921
Reviewed-By: Roman Reiss <me@silverwind.io>
Reviewed-By: Michaël Zasso <mic.besace@gmail.com>

lib/_http_server.js

@@ -2,7 +2,7 @@
 
 const util = require('util');
 const net = require('net');
-const EventEmitter = require('events').EventEmitter;
+const EventEmitter = require('events');
 const HTTPParser = process.binding('http_parser').HTTPParser;
 const assert = require('assert').ok;
 const common = require('_http_common');
@@ -117,7 +117,8 @@ function onServerResponseClose() {
   // array. That is, in the example below, b still gets called even though
   // it's been removed by a:
   //
-  //   var obj = new events.EventEmitter;
+  //   var EventEmitter = require('events');
+  //   var obj = new EventEmitter();
   //   obj.on('event', a);
   //   obj.on('event', b);
   //   function a() { obj.removeListener('event', b) }