jruby-gradle-jar-plugin is walking upright

In this changeset:
+ Jar task type extended with `jruby` closure
+ Ability to add custome gem directories
+ Ability to make a JAR executable using `warbler-bootstrap`
+ Ability to make A JAR executable supplying own main class
With asciidoctor I came across the usage of GEMs only for needd for testing. I am not openly going to use these additional configurations as yet, but would like to try them to see if the approach actually works. I woul dhave marked them `@Incubating` if ti as possible