Add rfft, irfft, hfft, ihfft. better errors.
Add rfft, irfft, hfft, ihfft. better errors.

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