Make src/xterm.js ES2015 and export EventEmitter into its own file

Fix #158

demo/app.js

@@ -7,7 +7,7 @@ var pty = require('pty.js');
 var terminals = {},
     logs = {};
 
-app.use('/src', express.static(__dirname + '/../src'));
+app.use('/build', express.static(__dirname + '/../build'));
 app.use('/addons', express.static(__dirname + '/../addons'));
 
 app.get('/', function(req, res){

demo/index.html

@@ -2,11 +2,11 @@
 <html>
     <head>
         <title>xterm.js demo</title>
-        <link rel="stylesheet" href="../src/xterm.css" />
+        <link rel="stylesheet" href="../build/xterm.css" />
         <link rel="stylesheet" href="../addons/fullscreen/fullscreen.css" />
         <link rel="stylesheet" href="style.css" />
       	<script src="https://cdnjs.cloudflare.com/ajax/libs/fetch/1.0.0/fetch.min.js"></script>
-        <script src="../src/xterm.js" ></script>
+        <script src="../build/xterm.js" ></script>
         <script src="../addons/attach/attach.js" ></script>
         <script src="../addons/fit/fit.js" ></script>
         <script src="../addons/fullscreen/fullscreen.js" ></script>