Render Phame templates in the expected order

Summary: Currently, content runs before header. Instead, run header, content, footer. This makes it easier to use `header.php` for includes, for Phacility.

Test Plan: Made Phacility blog work better, see next diff.

Reviewers: chad

Reviewed By: chad

Subscribers: epriestley

Differential Revision: https://secure.phabricator.com/D10067