Update asciidoctor-epub3 to 1.5.0-alpha.8
Update asciidoctor-epub3 to 1.5.0-alpha.8

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