Add nested and ordered lists to Remarkup
Summary:
This is kind of tricky. I think I got all the edge cases sorted, though. This
needs a companion update to Phabricator for styling and documentation.
See some more discussion in T885.
Test Plan:
Ran unit tests, played around with it in Phabricator and couldn't
find anything going wrong.
Reviewers: btrahan
Reviewed By: btrahan
CC: aran, epriestley
Maniphest Tasks: T885
Differential Revision: https://secure.phabricator.com/D1638