[BrowserKit] Use getInternalResponse instead of getResponse

I am using the `Laravel4` and `REST` modules and I have an issue with `seeResponseCodeIs` which is:

```
PHP Fatal error:  Call to undefined method Illuminate\Http\Response::getStatus() in /var/www/vendor/codeception/codeception/src/Codeception/Module/REST.php on line 606
```

The problem here is that the REST module expects a `Symfony\Component\BrowserKit\Response` but instead gets a `Symfony\Component\HttpFoundation\Response` which doesn't have a getStatusCode method.

The issue seems to come from the fact that the `Symfony\Component\BrowserKit\Client::getResponse()` in Symfony 2.3 returns the origin request object, and not a `Symfony\Component\BrowserKit\Response` object. There seems to be a new method in Symfony 2.3 thats called `Symfony\Component\BrowserKit\Client::getInternalResponse()` which returns a `Symfony\Component\BrowserKit\Response` object instead.

This issue seems to have come up in the past (see #174, #289 and maybe #486).

What I have done is replace `getResponse` calls with `getInternalResponse` calls instead.