Update README.adoc

Change `$render` to `$convert`
sync with upstream 1.5.0.rc.2 release

- compile against Asciidoctor 1.5.0.rc.2 release
- update stylesheet
- set compat-mode=legacy on example document
- import Google Fonts
Merge branch 'mojavelinux-sync-upstream' #39
Upgrade version to 1.5.0-rc.2