Get rid of the check for _hashed-* files; those files are gone gone gone.

Summary:
I deleted the code that produces them 2 months ago.

I also added support for the new third_party directory I want to create.

Test Plan: Fingers crossed.

Reviewers: alpert, eater

Reviewed By: alpert

Differential Revision: http://phabricator.khanacademy.org/D4424