Bump remarkup engine version for new list stuff

Summary: Fixes T5102. Bumps the version to clear caches and documents the `#` headers.

Test Plan: Read documentation.

Reviewers: asherkin, btrahan, chad

Reviewed By: chad

Subscribers: epriestley

Maniphest Tasks: T5102

Differential Revision: https://secure.phabricator.com/D10046