Verifier responds to GET with 404 instead of 405

[callahad]

GET https://verifier.login.persona.org/verify should totally not return a 404 Not Found.

405 Method Not Allowed seems more reasonable.

[rfk]

FWIW the "new verifier" at https://github.com/mozilla/browserid-verifier handles this with a 405 already. I wonder if we should try to push forward with migrating persona.org over to that new codebase, to share both dev and infra costs?