Add doctest for old style classes.

Descriptors are invoked via the __getattribute__ method, which is only
available for new-style classes. Therefore old style classes require
extra testing. See:

http://docs.python.org/2/howto/descriptor.html#invoking-descriptors
Fix old-style classes [HOT]
Merge branch 'master' into hotfix-oldstyle-classes

Conflicts:
	setup.cfg

This branch has been pending for a while, thus a merge of the current master
branch was required for conflict resolution.