resolves #28 create asciidoc vs asciidoctor page

- added link to docs index page
- sorted differences into categories
- added next steps section

This document includes all the comparison information from the README.
It does not yet include any new or missing information, however I'm closing the issue with this pull request because the issue is too broad.

New issues should be spawned to:

1. review and update this doc per 0.1.2 
2. review and update this doc per 0.1.3

Next step: Remove the comparison from the websites homepage.