pep8 whitespace fix
pep8 cleanup this test

All the tests need this, but just doing this one for now since
it had a recent visit.
remove unused import

With migration of timestamp code to model.tiddler import of time
no longer needed.
Adjust timestamp handling so default is encapsulated on model.tiddler

Otherwise we have two different places where we declare that
datetime.utcnow() is the default.