Work done by @guyboertje and @ph
Since JRuby 1.7.25 is now EOL we are migrating Logstash to use JRuby 9k and JDK8 only,
Not much needed updating to make this work, its was mostly a drop in replacement from the previous version.
The major point was the change in the implementation of Time in JRuby, JRuby now use `java.time`
instead of joda time, this allow JRuby to have nanoseconds precision on time object.