Handle obsolete biblios too

[tabatkins]

Tobie just added obsoletion information to SpecRef in tobie/specref#199.

Specs can now have an "obsoletes" key (pointing to the spec they're obsoleting) and/or an "obsoletedBy" key, pointing to the spec that obsoleted them.

I should throw a fatal error when someone tries to biblio-ref an obsolete spec, and tell them which spec to change their reference to.

[frivoal]

+1 on the need to support that feature, and on the way you propose to handle it. Any chance it would happen before long, or should I learn some python and try and figure out how to make that happen myself?

[tabatkins]

Ah, this just slipped down my prio list. Shouldn't be difficult to do.

[tabatkins]

And done.