small optimization of bivariate moran motivated by #695
small optimization of bivariate moran motivated by #695

jlaura/pysal,schmidtc/pysal,hasecbinusr/pysal,TaylorOshan/pysal,hasecbinusr/pysal,pastephens/pysal,TaylorOshan/pysal,lixun910/pysal,ljwolf/pysal_core,sjsrey/pysal_core,ljwolf/pysal,sjsrey/pysal_core,pastephens/pysal,pastephens/pysal,chhao91/pysal,ljwolf/pysal,lixun910/pysal,sjsrey/pysal,schmidtc/pysal,chhao91/pysal,ljwolf/pysal,sjsrey/pysal_core,lixun910/pysal,ljwolf/pysal_core,pedrovma/pysal,jlaura/pysal,jlaura/pysal,lanselin/pysal,pysal/pysal,TaylorOshan/pysal,weikang9009/pysal,hasecbinusr/pysal,ljwolf/pysal_core