MCRYPT_RIJNDAEL_256 wants 16 byte key in php 5.6

Current key produces this exception:
```
at HandleExceptions->handleError('2', 'mcrypt_encrypt(): Key of size 13 not supported by this algorithm. Only keys of sizes 16, 24 or 32 supported', '/Users/jwood/Documents/projects/uscompliance.com/training-center/vendor/platforg/adobe-connect/src/AdobeConnect/Connection.php', '135', array('cookie' => object(SimpleXMLElement), 'this' => object(Connection)))
at mcrypt_encrypt('rijndael-256', '7e2d20j23a21d', 'na8breezu6k4xazhvktcaiqw', 'ecb', 'gseac') in Connection.php line 135
```