Enhancements

#45 - added parameter persist_defaults to UserProperty. If this parameter is set to True and a UserProperty also has either the default or default_function parameter , when the UserProperty returns a default value that value will also be explicitly stored in the underlying data object. This was the default behavior before 0.1.4. This is often desirable behavior if the UserProperty returns another object and your code expects it to return the same object instance each time it is accessed, and so is now provided as a configurable parameter.

Bug fixes

#42 - default values of a UserProperty will now be returned as the type declared in property_type, as before 0.1.4