refactor: migrate to ES6 syntax

Author: darrachequesne

lib/index.js

@@ -1,10 +1,14 @@
+const Socket = require('./socket');
 
-module.exports = require('./socket');
+module.exports = (uri, opts) => new Socket(uri, opts);
 
 /**
- * Exports parser
- *
- * @api public
- *
+ * Expose deps for legacy compatibility
+ * and standalone browser access.
  */
+
+module.exports.Socket = Socket;
+module.exports.protocol = Socket.protocol; // this is an int
+module.exports.Transport = require('./transport');
+module.exports.transports = require('./transports/index');
 module.exports.parser = require('engine.io-parser');