R1:025b243e2741

Document wiki relative link syntax

Summary: Also make `../` work to start relative a link so I don't have to document it as `./../path`.

Test Plan:
- Used `./`, `../`. `./../`, and normal links (proper title pickup).
- Used bad links (red).
- Regenerated documentation:

{F1221692}

Reviewers: hach-que

Reviewed By: hach-que

Differential Revision: https://secure.phabricator.com/D15734