Fixes to text input review mode.

Summary: These are changes from an audit by Aria.

Test Plan:
Went through several sections of the SAT mission with review mode
forced on.

Reviewers: aria

Reviewed By: aria

Differential Revision: http://phabricator.khanacademy.org/D14512
Group widgets now trigger onInteractWithWidget.

Test Plan:
Clicked on a radio button in a group widget and observed the top level
renderer's onInteractWithWidget callback fire.

Reviewers: alex, aria

Reviewed By: aria

Subscribers: #sat, eater, dylan

Differential Revision: http://phabricator.khanacademy.org/D14568