More Cryptographically-Secure Salt Generator.

As seen on the [PHP: mt_rand](http://php.net/manual/en/function.mt-rand.php) page:

>[`mt_rand()`] does not generate cryptographically secure values, and should not be used for cryptographic purposes. If you need a cryptographically secure value, consider using `openssl_random_pseudo_bytes()` instead.

This pull request implements `openssl_random_pseudo_bytes()` for salt generation.