R1:4549afbdce54

Link Ponder Answer header to user

Summary: Fixes T9509

Test Plan: View a Ponder Question, hover over answerer name, get URL.

Reviewers: epriestley

Reviewed By: epriestley

Subscribers: Korvin

Maniphest Tasks: T9509

Differential Revision: https://secure.phabricator.com/D14238