Use geoip jars gem

I've removed the bundled JAR files, both geoip-api and jgeoip. The geoip-api has been updated to 1.2.12.

I removed geoip-api and instead made the gem depend on [geoip-jars](http://rubygems.org/gems/geoip-jars), that way the GeoIP library can be updated independently of jgeoip (I was going to just update to 1.2.12, but I figured I might as well do this while I was at it).

I've also removed the jgeoip-*.jar files that were checked in. Mostly because it feels like having two different versions checked in an bundled in the gem is an accident waiting to happen.

The downside of not having it checked in is that you can't depend on the gem directly from git. On the other hand you'd have to rebuild the JAR anyway to be able to do that, and then you could just as well push up a prerelease gem.

The reason I wanted to update to 1.2.12 is that the versions before it have some bugs that made them crash for most IPs in the 223.255.254.0/24 range when using `GEOIP_INDEX_CACHE`.