minor optimizations in HTML5 converter
minor optimizations in HTML5 converter

yukisan/asciidoctor,cuit-zhaxin/asciidoctor,benignbala/asciidoctor,neontapir/asciidoctor,yukisan/asciidoctor,anthonny/asciidoctor,gjtorikian/asciidoctor,glamouracademy/asciidoctor,pepijnve/asciidoctor,gjtorikian/asciidoctor,anthonny/asciidoctor,neontapir/asciidoctor,cuit-zhaxin/asciidoctor,glamouracademy/asciidoctor,mjang/mj-asciidoc,asciidocfx/asciidoctor,mjang/mj-asciidoc,pepijnve/asciidoctor,asciidocfx/asciidoctor,benignbala/asciidoctor