ED URLs

Hi,

Seems like we're going to be able to get ED urls directly from the W3C RDF
file soonish.

Would like your thoughts on how to best integrate that in the Specref API.

I see two options:

1. Pass an extra query param to specify what you want, e.g.:

http://specref.jit.su/bibrefs?refs=service-workers&type=ED|TR|LATEST

Which would give you, respectively:

- https://slightlyoff.github.io/ServiceWorker/spec/service_worker/
- http://www.w3.org/TR/service-workers/
- http://www.w3.org/TR/2014/WD-service-workers-20140508/

This has the benefit that ReSpec could be smart about it and pick ED when
the spec is in ED, but change to TR for publishing WDs for example.

2. Automatically generate extra references, e.g.:

http://specref.jit.su/bibrefs?refs=service-workers-ED
http://specref.jit.su/bibrefs?refs=service-workers-TR
http://specref.jit.su/bibrefs?refs=service-workers-LATEST ?

We could also do a mix of both.

LMK your thoughts.

--tobie