3 - Split main functionality out of sugar sub class_has(), into
4 process_class_attribute(). This makes it easier to create attributes
5 on behalf of other classes.
10 - Inherit from Exporter, rather than trying to import its
11 import(). Unfortunately, older Exporters as shipped with Perl 5.6.x
12 only allow subclassing.
17 - First version, released on an unsuspecting world.