Always use absolute URIs for static resources

Summary: I think this is simpler and better than making them conditional. In properly configured installs this should have no impact (they already use a CDN URI). In not-quite-properly configured installs this will add a trivial, highly-compressible number of bytes to the source. In all cases we have less code.

Test Plan: Loaded some pages, everything worked.

Reviewers: btrahan, vrana

Reviewed By: vrana

CC: aran

Differential Revision: https://secure.phabricator.com/D3709