Added support for age range.

[mhverbakel]

Fixes #217.

[coveralls]

Coverage remained the same at 100.0% when pulling b9da85f on mhverbakel:master into 90a642b on jaredhanson:master.

[rwky]

Merged in https://github.com/passport-next/passport-facebook

[jaredhanson]

Passport tries to keep profiles normalized to the Portable Contacts schema, or extensions to it such as OpenSocial. The simplifies integration of multiple social providers, by avoiding things that may be specific to an IdP like Facebook.

IdP-specific attributes are always available via profile._json. I'd consider merging this if there were a clear convention around age range support across IdPs.