inspect.getmembers and inspect.classify_class_attrs now search the metaclass
mro for types.DynamicClassAttributes (what use to be called
enum._RouteClassAttributeToGetattr); in part this means that these two
functions no longer rely solely on dir().

Besides now returning more accurate information, these improvements also
allow a more helpful help() on Enum classes.

Also slight code reorg for PEP 8 guidelines.

Before this change only the methods were _single_underscored_; now
the attributes are as well.

The docs also clarify the 'Interesting Example' duplicate-free enum is for
demonstration purposes.

Missing files added.
News entry added.