Clear mock notifications when viewing mocks

Summary:
- When viewing a mock, clear unread flag on notifications about it.
  - Show the "lcick to reload" version of the popup when you get a notification about the current mock.

Test Plan: Clicked a notification to clear it.

Reviewers: chad

Reviewed By: chad

CC: aran

Differential Revision: https://secure.phabricator.com/D5055