0.3.0-pre.4

Added:

• NonconformantDocument object as a fallback when all other validation fails. It attempts to make the resulting document as usable as possible without making assertions about what is or is not present in the document. Use pydid.deserialize_document(value) to get this fallback behavior. Use pydid.deserialize_document(value, strict=True) to keep strict validation behavior.
• Various fixes discovered while improving test coverage.