Refactor negative step slicing
Refactor negative step slicing

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