fix ipv6 support for geoip

Simple fix to support the IPv6 databases in the filter.

Fixes 
- https://logstash.jira.com/browse/LOGSTASH-1100

and partly
- https://logstash.jira.com/browse/LOGSTASH-1124
- https://logstash.jira.com/browse/LOGSTASH-2163

reworked from https://github.com/elasticsearch/logstash/pull/1350
Direct downloads from maxmind will be blocked because they don't like regular downloads.
We will be copying the files over to one of our local S3 buckets and serve it from there.
Thanks though for the link, this way we know where to pull it from :-)
Will modify it after merge.