Changed createPHPExcelObject to pass filename as a string to fix Context...

...ErrorException

$phpExcelObject = $this->get('phpexcel')->createPHPExcelObject('file.xls') fails with ContextErrorException: Warning: pathinfo() expects parameter 1 to be string, array given in vendor/phpoffice/phpexcel/Classes/PHPExcel/IOFactory.php line 224 (Symfony 2.4, PHP 5.5.6).