Document norm in Dask Array API (#2605)
Document norm in Dask Array API (#2605)

Makes sure that norm shows up in Dask Array's API.

[ci skip]
blaze/dask,ContinuumIO/dask,jakirkham/dask,jakirkham/dask,mrocklin/dask,jcrist/dask,ContinuumIO/dask,dask/dask,blaze/dask,jcrist/dask,dask/dask,mrocklin/dask