Add a bunch of additional test cases for ArcanistTextLinter

Summary: Self-explanatory, improve test coverage.

Test Plan: Wrote and executed unit tests.

Reviewers: Blessed Reviewers, epriestley

Reviewed By: Blessed Reviewers, epriestley

Subscribers: epriestley, Korvin

Differential Revision: https://secure.phabricator.com/D10474