Update documentation and CSS for nested and enumerated lists

Summary: Update Phabricator for Remarkup changes in D1638.

Test Plan: Looked at various sorts of nested, enumerated, and phantom-item
lists.

Reviewers: btrahan, jungejason

Reviewed By: jungejason

CC: aran, epriestley

Maniphest Tasks: T885

Differential Revision: https://secure.phabricator.com/D1639