Make Phriction edits show in the feed.

Summary: Add a WIKI block to the switch in PhabricatorObjectHandleData->loadObjects().

Test Plan: Went to /feed/ and saw my wiki edit stories.

Reviewers: epriestley

Reviewed By: epriestley

CC: aran, Korvin

Differential Revision: https://secure.phabricator.com/D4180