Fix renderer and move notice of remaining parts

Summary:
This fixes the problems that came up with wrapping the question area
renderer in a div.

The fix sidesteps the issue entirely by following a suggestion from
Marcos to move the "parts remaining" thing into the answer area. Even
thought that's going away, I think it makes more sense for the time being,
since that's closer to the "check answer" button

Test Plan:
* Open a perseus question
* Should be able to score it
* subperseus
* Open a perseus question in webapp
* should not get any errors

Reviewers: jack

Reviewed By: jack

Subscribers: alpert

Differential Revision: http://phabricator.khanacademy.org/D7587