resolves #232 by rising an AsciidoctorCoreException in case of Asciidoctor Ruby Runtime exception.
Merge branch 'master' of https://github.com/asciidoctor/asciidoctorj
upgrade JRuby and JRuby plugin

- upgrade JRuby to 1.7.17
- upgrade JRuby plugin to 0.1.10
- tweak Gradle build to allow tests to be run on JDK6
- reenable openjdk6 in build matrix
Merge pull request #241 from mojavelinux/jruby-upgrade

upgrade JRuby and JRuby plugin