Improve robustnesss of feed text rendering

Summary:
Couple of minor cleanup things here:

• Pass handles to ApplicationTransactions when rendering their stories; this happened implicitly before but doesn't now.
• Add ?text=1 to do ad-hoc rendering of a story in text mode.
• Make Conduit skip unrenderable stories.
• Fix/modernize some text in the Commit story.

Test Plan: Rendered text versions of stories via Conduit and ?text=1.

Reviewers: btrahan, chad

Reviewed By: chad

Subscribers: zeeg, spicyj, epriestley

Differential Revision: https://secure.phabricator.com/D8793