add dataframe groupby methods to api docs (#2187)
add dataframe groupby methods to api docs (#2187)


dask/dask,ContinuumIO/dask,mraspaud/dask,blaze/dask,mraspaud/dask,jcrist/dask,ContinuumIO/dask,blaze/dask,jcrist/dask,cpcloud/dask,mrocklin/dask,jakirkham/dask,jakirkham/dask,mrocklin/dask,dask/dask