Move the toby nginx configs over to the nginx_site_* regime.

Summary:
This is what the other machines use.  I think it makes it easier to
see all the nginx stuff that's going on, and makes it so you don't
have to manage the available/enabled symlinks by hand.

Test Plan: Fingers crossed.

Reviewers: chris

Reviewed By: chris

Differential Revision: http://phabricator.khanacademy.org/D14533