implement login 3.0

https://bugzilla.mozilla.org/show_bug.cgi?id=1090285
Yes, because our CDN is configured to send all traffic with `/auth` to this server, and the rest to S3: https://www.dropbox.com/s/337a23wzkk4xl34/Screenshot%202014-10-30%2015.17.12.png?dl=0