Added delay to open command

This is needed if page's content is generating using javascript. So you should wait few seconds until all data will be loaded.

Request a URL with delay and output the reponse:

```php
<?php

use JonnyW\PhantomJs\Client;

$client = Client::getInstance();

/** 
 * @see JonnyW\PhantomJs\Message\Request 
 **/
$request = $client->getMessageFactory()->createRequest('GET', 'http://google.com');

/** 
 * @see JonnyW\PhantomJs\Message\Response 
 **/
$response = $client->getMessageFactory()->createResponse();

// Send the request with delay in miliseconds
$client->open($request, $response, $delay = 5000);

if($response->getStatus() === 200) {
	
	// Dump the requested page content
	echo $response->getContent();
}
```