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