Added support for ipv6

Changed the way the IP is cached to use a hex of the IP which is generated from a new method called ipToHex
Also added the FILTER_FLAG_IPV6 to the validateIp method.
Also added geoplugin_cached to the response for easily checking if the IP is in the cache
Finally, modified the 404 response detection to check if the geoplugin_status property isset in the response.