Increase the pin_reponse field size to accomodate larger response sizes

The field pin_response was too low to incorporate all responses from the server.

For example the response 'No resource was found at this URL. See https://pin.net.au/docs/api for API documentation and a list of valid URLs.' was received which contains 114 characters.

The field size should be increased accordingly to allow this. It has been set to 255 cautiously to allow future responses.