Add a simple gradle file for building this plugin as a standalone plugin
Add a simple gradle file for building this plugin as a standalone plugin

<http://www.gradle.org/docs/current/userguide/custom_plugins.html#N167CE>

MisumiRize/jruby-gradle-plugin,mkristian/jruby-gradle-plugin,jamescway/jruby-gradle-plugin,MisumiRize/jruby-gradle-plugin,raelik/jruby-gradle-plugin,mkristian/jruby-gradle-plugin,MisumiRize/jruby-gradle-plugin,jamescway/jruby-gradle-plugin,raelik/jruby-gradle-plugin,jamescway/jruby-gradle-plugin,raelik/jruby-gradle-plugin