R1:d90a6cfbd1a1

Move files in notification one level up.

Summary: Moved the files in notification one level up to match the rest of code base. And ran arc liberate.

Test Plan: Made sure __phutil_library_map__ points to the right files.

Reviewers: epriestley, btrahan

Reviewed By: epriestley

CC: allenjohnashton, aran, Korvin

Differential Revision: https://secure.phabricator.com/D2688