Added sniff that detects if an entity implements the automatically generated interface

Also made the project compatible with PHP 5.4 again
Can you make a guard clause of this? This will break the loop and makes reading a lot easier, the else will no longer be necessary. `$code` can also be re-used easily.

```php
$code = $phpcsFile->getTokens()[$interface_name]['code'];
if (!in_array($code, [T_STRING, T_NS_SEPARATOR])) {
    break;
}
```