Todo
====

* Whenenever the XML element is empty, the value of the object should
  not be None but the default object that the schema indicates.

* What to do when importing something that has no XML but is required
  according to the schema. Error?

* Add an option to serialization that does not generate XML element if the
  content of the object is equal to the schema default.

* test adapter lookup failure

* test whether GeneratedObject implements right schema interface.

* test without explicit __name__ for Lists. What should happen? Fallback
  on interface name?

* test deserialization on an empty object.

* what to do in case of a missing element in an XML document?

* form data file instances need to provide schema

Punt
----

* custom factories instead of GeneratedObject.

* What to do with XML namespaces?
