Require geoip >= 1.3.2 to fix LOGSTASH-1394.

The new geoip version defines to_hash on GeoIP::ASN objects.
Merge pull request #694 from bernd/LOGSTASH-1394

Fix geoip filter with GeoLite ASN database. (LOGSTASH-1394)
Merge git://github.com/logstash/logstash