Summary:
Migrate to the new hotness. Also:
- Remove a string test, which is now impossible since the config will repair itself and raise a type error.
- Restore the header even in /config/ -- this check is kind of hacky and it feels a bit more natural now that it's above the menu.
Test Plan: Set my local disk path to something invalid, verified I got a setup error.
Reviewers: btrahan, vrana
Reviewed By: btrahan
CC: aran
Maniphest Tasks: T2228
Differential Revision: https://secure.phabricator.com/D4497
