check for negative slices in normalize
check for negative slices in normalize

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