Adjust KickBox client for API changes

The response fields "role", "free", "disposable" and "accept_all" are not booleans instead of strings:

```php
array(13) {
  'result' =>
  string(5) "valid"
  'reason' =>
  string(14) "accepted_email"
  'role' =>
  bool(true)
  'free' =>
  bool(true)
  'disposable' =>
  bool(true)
  'accept_all' =>
  bool(true)
  'did_you_mean' =>
  NULL
  'sendex' =>
  int(0)
  'email' =>
  string(22) "test@guerrillamail.com"
  'user' =>
  string(4) "test"
  'domain' =>
  string(17) "guerrillamail.com"
  'success' =>
  bool(true)
  'message' =>
  NULL
}
```