skip df test if no pandas
skip df test if no pandas

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