Fix Hash type casting

When using comparison with a boolean, as the filter is a string, we have to convert the data boolean to "boolean string" to avoid type-casting troubles.

## Example
```php
$users = [
    [
        'id' => 2,
        'username' => 'johndoe',
        'active' => true
    ],
    [   'id' => 5,
        'username' => 'kevin',
        'active' => true
    ],
    [
        'id' => 9,
        'username' => 'samantha',
        'active' => false
    ],
];
$unactiveUsers = Hash::extract($users, '{n}[active=false]');
print_r($unactiveUsers);
```

This example returns the two unwanted active users because `"false"` is `true` but not `false` :)

I think this pull request will fix this issue by converting true/false boolean to string (to match with our filter).