Contains Dockerfiles for building images for JRuby on a couple of JVM versions for testing on Circle CI.
Based on the Dockerfiles in https://github.com/cpuguy83/docker-jruby and the JRuby Dockerfiles in https://github.com/CircleCI-Public/circleci-dockerfiles
This is all in aid of testing https://github.com/fidothe/saxon-rb on Circle CI.