Add tests for bag.from_s3
Add tests for bag.from_s3

pombredanne/dask,cpcloud/dask,gameduell/dask,mrocklin/dask,mikegraham/dask,jcrist/dask,PhE/dask,jakirkham/dask,dask/dask,wiso/dask,dask/dask,ssanderson/dask,ContinuumIO/dask,vikhyat/dask,blaze/dask,mraspaud/dask,mrocklin/dask,chrisbarber/dask,jayhetee/dask,vikhyat/dask,wiso/dask,jakirkham/dask,simudream/dask,pombredanne/dask,PhE/dask,ContinuumIO/dask,freeman-lab/dask,clarkfitzg/dask,clarkfitzg/dask,blaze/dask,freeman-lab/dask,mraspaud/dask,cowlicks/dask,simudream/dask,jayhetee/dask,jcrist/dask,ssanderson/dask