Reduce size of dataframes
Reduce size of dataframes

A recent commit expanded the size of the dataframes here in this test,
causing timeout errors.

It takes a long time because we're creating n**2 groups

dask/distributed,blaze/distributed,mrocklin/distributed,amosonn/distributed,dask/distributed,blaze/distributed,mrocklin/distributed,amosonn/distributed,broxtronix/distributed,broxtronix/distributed,amosonn/distributed,dask/distributed,dask/distributed,broxtronix/distributed,mrocklin/distributed