Sort Ponder Answers by voteCount

Summary: Fixes T9207. I think this is correct? Sorts based on vote count and reverses the order of the array so higher is first.

Test Plan: Test vote ordering on a number of sample tasks.

Reviewers: epriestley

Reviewed By: epriestley

Subscribers: Korvin

Maniphest Tasks: T9207

Differential Revision: https://secure.phabricator.com/D13924