drop sudo: false from Travis CI config
drop sudo: false from Travis CI config

remove sudo: false (container-based infrastructure) as recommended by Travis

dsisnero/asciidoctor-pdf,mojavelinux/asciidoctor-pdf,Hextremist/asciidoctor-pdf,Hextremist/asciidoctor-pdf,asciidoctor/asciidoctor-pdf,asciidoctor/asciidoctor-pdf,dsisnero/asciidoctor-pdf,mojavelinux/asciidoctor-pdf