make PonderQuestionQuery policy aware

Summary: wanted to play with some policy stuff as its been a bit. Turns out you can't edit questions so this is very silly "so long as you are a user you can view it" policy. also sorry if you have a diff or twelve out for this in your sandbox(es).

Test Plan: loaded up ponder and clicked about

Reviewers: epriestley

Reviewed By: epriestley

CC: aran, Korvin

Maniphest Tasks: T2113

Differential Revision: https://secure.phabricator.com/D4163