Add in top spacing for Perseus on XOM
Add in top spacing for Perseus on XOM

Test Plan:
 - tbd: this requires the the host `webapp` apply the
 `perseus-xom-manateee` class on exercises

Reviewers: charlie

Reviewed By: charlie

Subscribers: jared

Differential Revision: https://phabricator.khanacademy.org/D27921

ariabuckles/perseus,ariabuckles/perseus,ariabuckles/perseus,learningequality/perseus,learningequality/perseus,ariabuckles/perseus