change producer example in readme
change producer example in readme

thedrow/samsa,wikimedia/operations-debs-python-pykafka,aeroevan/pykafka,benauthor/pykafka,jofusa/pykafka,wikimedia/operations-debs-python-pykafka,thedrow/samsa,benauthor/pykafka,yungchin/pykafka,sammerry/pykafka,wikimedia/operations-debs-python-pykafka,thedrow/samsa,benauthor/pykafka,aeroevan/pykafka,yungchin/pykafka,sammerry/pykafka,jofusa/pykafka