Summary:
Added a typeahead in the edit herald rule page that allows an admin or
owner to change the current owner of a rule. If the typeahead is emptied, the
current owner will remain owner.
Test Plan:
Created a test rule. Changed the owner. Deleted the owner in the
typahead. Verified expected behavior.
Reviewers: jungejason, epriestley
Reviewed By: epriestley
CC: aran, jungejason, epriestley, xela
Differential Revision: https://secure.phabricator.com/D1322
