use modern syntax in CONTRIBUTING; add note about verbose mode
use modern syntax in CONTRIBUTING; add note about verbose mode

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