added doctests to esda/interaction
added doctests to esda/interaction

TaylorOshan/pysal,schmidtc/pysal,ljwolf/pysal_core,jlaura/pysal,sjsrey/pysal_core,chhao91/pysal,sjsrey/pysal_core,darribas/pysal,pedrovma/pysal,pastephens/pysal,sjsrey/pysal_core,hasecbinusr/pysal,hasecbinusr/pysal,ljwolf/pysal,darribas/pysal,jlaura/pysal,TaylorOshan/pysal,ljwolf/pysal,spreg-git/pysal,lanselin/pysal,spreg-git/pysal,badjr/pysal,weikang9009/pysal,chhao91/pysal,pastephens/pysal,sjsrey/pysal,dfolch/pysal,lixun910/pysal,ljwolf/pysal_core,badjr/pysal,ljwolf/pysal,TaylorOshan/pysal,pastephens/pysal,lixun910/pysal,pysal/pysal,ljwolf/pysal_core,lixun910/pysal,dfolch/pysal,nathania/pysal,schmidtc/pysal,hasecbinusr/pysal,nathania/pysal,jlaura/pysal