fix parameter name for traversing to a portal, close #95
as of plone.testing 4.0.8, ACTUAL_URL is prepared for us, no need to manually set it any more, refs #92
confirm that the record exists before setting the value
Fix datetime format in tests.

The api.portal.localized_time can return different datetime formats on
different systems, causing test failures on only a subset of machines.

Therefore, before testing the localized_time() method, we set the expected
datetime format portal-wide.
tests in .rst files should be very minimal