rename workers to nannies in dworker
rename workers to nannies in dworker

broxtronix/distributed,amosonn/distributed,mrocklin/distributed,dask/distributed,dask/distributed,mrocklin/distributed,amosonn/distributed,mrocklin/distributed,dask/distributed,dask/distributed,broxtronix/distributed,blaze/distributed,broxtronix/distributed,blaze/distributed,amosonn/distributed