update_status: first positional argument should be 'status'
Passing the tweet text as the lone positional argument to update_status: api.update_status(u'Hi mum!') is suggested in much documentation and in several tests, but f99b1da5 introduced media_ids as the first argument, breaking this API. This change will break anyone who uses tweepy >= 3.2 and assumes they can pass media_ids as the first positional; but I expect that to be a much smaller set than people who have followed the example in the docs, who find their application mysteriously fails to post tweets after upgrading tweepy. Fixes #554.