add memory use note to tsqr docstring
add memory use note to tsqr docstring

jakirkham/dask,jcrist/dask,mrocklin/dask,chrisbarber/dask,jakirkham/dask,cowlicks/dask,mrocklin/dask,cpcloud/dask,dask/dask,mraspaud/dask,blaze/dask,blaze/dask,mraspaud/dask,dask/dask,ContinuumIO/dask,ContinuumIO/dask,jcrist/dask,gameduell/dask