Add HTTPS now

Hello,

I’d like to ask to update the plugin adding a letter s within the http://:

	// Send back the completed tag
	return '<img src="https://www.gravatar.com/avatar/' . md5( trim( strtolower( $email ) ) ) . '.jpg?s=' . $size . $rating . $default . '" width="' . $size . '" height="' . $size . '"' . $alt . $title . $align . $style . $class . $id . $border . ' />';
}

Great plugin. That is why I use it! ⚡️ 👍 🏆

Kind regards,