Don't penalize non-simplification unless specifically configured to do so

Test Plan: http://localhost:8000/utils/test/answer-types.html and testing unsimplified answers in adding_fractions and simplifying_fractions to verify proper behavior in local mode

Reviewers: alex

Reviewed By: alex

CC: alpert

Differential Revision: http://phabricator.khanacademy.org/D4262