apply workaround for travis build with openjdk 7
apply workaround for travis build with openjdk 7

See https://github.com/travis-ci/travis-ci/issues/5227 for more information

robertpanzer/asciidoctorj,lefou/asciidoctorj,abelsromero/asciidoctorj,ysb33r/asciidoctorj,abelsromero/asciidoctorj,ysb33r/asciidoctorj,ysb33r/asciidoctorj,asciidoctor/asciidoctorj,robertpanzer/asciidoctorj,lefou/asciidoctorj,abelsromero/asciidoctorj,asciidoctor/asciidoctorj,robertpanzer/asciidoctorj,asciidoctor/asciidoctorj,lefou/asciidoctorj,ysb33r/asciidoctorj,lefou/asciidoctorj