Code review comment for lp:~leonardr/lazr.restful/double-your-enjoyment

This branch creates a new doctest, multiversion.txt, which defines a web service that serves three distinct services ("beta", "1.0", and "dev") from a single underlying data model. Currently there is no code that uses this data model with lazr.restful, which is good because as soon as I add that code lazr.restful is going to explode. I'm submitting this branch as a natural stopping point before I have to start tearing up lazr.restful and putting it back together.

I'm using webservice.txt as a model for multiversion.txt. This is a little tricky because webservice.txt is a very old service that reimplements many of the niceties found in lazr.restful.simple. So I'm trying to improve webservice.txt as I copy it. For instance, I removed the Traversable class from webservice.txt and replaced it with the standard TraverseWithGet class. I also got rid of an XXX that said to make a certain change once we upgraded to zope 3.4.

I also tried to get rid of webservice.txt's BaseAbsoluteURL class, but it turned out to be way too much work. I'll just use ILocation in the new service and change webservice.txt later.