Fixed Pholio stories in feed.

Summary: Pholio stories now reference the mock they're talking about.

Test Plan: Generate each type of story and check that they make sense in feed/inline.

Reviewers: epriestley

Reviewed By: epriestley

CC: aran, Korvin, AnhNhan

Maniphest Tasks: T2988

Differential Revision: https://secure.phabricator.com/D6117