add cache to diagnostics/__init__.py
add cache to diagnostics/__init__.py

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