[PROPOSAL] Handle "http://user at example.com" Style Identifiers

[David Nicol]

> However, AOL can use http://username@aol.com/ so that their users are
> able to enter their identifier. AOL can even call those things email
> addresses if they want, because in AOL's namespace they are (presumably)
> guaranteed to match. But neither the OpenID Spec nor marketing materials
> should start running around saying "look! we accept email addresses
> too!" as that's just going to cause confusion.