Add tests for fft and ifft
Add tests for fft and ifft

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