Support logged-out users in Fund

Summary: Ref T5835. Sprinkle shouldAllowPublic() around to let logged-out users gain access.

Test Plan: Viewed an initiative while logged out.

Reviewers: btrahan

Reviewed By: btrahan

Subscribers: epriestley

Maniphest Tasks: T5835

Differential Revision: https://secure.phabricator.com/D10683