Support `datetime.timedelta` as a valid wait unit type (#342) * Support `datetime.timedelta` as a valid wait unit type Signed-off-by: Noam Bloom <nbloom5@bloomberg.net> * Add datetime.timedelta support tests Signed-off-by: Noam Bloom <nbloom5@bloomberg.net> Co-authored-by: Noam Bloom <nbloom5@bloomberg.net> Co-authored-by: Julien Danjou <julien@danjou.info>