Detect trailing spaces and tabs

Summary: Ref T12655 - this change properly detects trailing spaces or tabs (or combinations of thereof) on end of lines.

Test Plan: Use Text lint with trailing whitespace rule on files with spaces, tabs or combinations of thereof. Should properly detect and fix all those.

Reviewers: epriestley, Blessed Reviewers

Reviewed By: epriestley, Blessed Reviewers

Subscribers: Korvin, Itms

Maniphest Tasks: T12655

Differential Revision: https://secure.phabricator.com/D17814