Clean whitespace in blend user units.
Add setup.cfg with default options for flake8.
Add common flake8 ignores.

Arguably, I disagree with some of the style that flake8 wants to apply.
This is the beginning of ignoring those specifications.  If anyone wants
to make arguments for why these should be followed I'd enjoy hearing
them.
Fix super invocation's class.  Article → Tag.
Add E123 to flake8 ignores.
Add missing imports to spread user units.
Fix super class invocation: '' → Test
Fix naming, account → properties.
Fix super class, '' → Test
Add missing import of datetime.
Remove spurious whitespace.
Remove extra newline.
Remove extra newline.
Remove extra newline.
Add E261 to flake8 ignores.
Remove extra newline.
Remove spurious whitespace.