Move getPEP8WithTextOptions method into ComprehensiveLintEngine class.

Summary: Since this method is only used within this class, it makes sense to move it here.

Test Plan: N/A

Reviewers: epriestley, Blessed Reviewers

Reviewed By: epriestley, Blessed Reviewers

Subscribers: epriestley, Korvin

Differential Revision: https://secure.phabricator.com/D9114