Initial review

The most recent commit message is so accurate.

IIRC it's not very obvious from the pyramid docs, but `config.registry` provides a simple dict-like interface that's useful here.  For example, we use it for stashing the storage backend objects in sync like this:

https://github.com/mozilla-services/server-syncstorage/blob/master/syncstorage/storage/__init__.py#L478

Then grab them out from the incoming request object like this:

https://github.com/mozilla-services/server-syncstorage/blob/master/syncstorage/storage/__init__.py#L448

IMHO it's a very nice pattern for simplifying testing and code re-use, compared to singleton global variables.