Emit more usable results from phrequent.tracking

Summary:
I think this pretty much does what you would expect?

The "active" item is always at the top of the stack.

Test Plan: Called `phrequent.tracking` and got reasonable results.

Reviewers: hach-que

Reviewed By: hach-que

Subscribers: epriestley

Differential Revision: https://secure.phabricator.com/D9939