Added JSON_UNESCAPED_UNICODE and JSON_UNESCAPED_SLASHES to encoding APNS Data to JSON

As APNS documentation says "The payload must not exceed 256 bytes and must not be null-terminated" so inefficiently to use escaped unicode characters and slashes:
```php
php > echo json_encode("{'key1':'Привет,/ГитХаб/'}");
# "{'key1':'\u041f\u0440\u0438\u0432\u0435\u0442,\/\u0413\u0438\u0442\u0425\u0430\u0431\/'}"
# Lenght: 90
```

```php
php > echo json_encode("{'key1':'Привет,/ГитХаб/'}", JSON_UNESCAPED_UNICODE | JSON_UNESCAPED_SLASHES);
# "{'key1':'Привет,/ГитХаб/'}"
# Lenght: 40
```