tweaking travis to only run master commits
tweaking travis to only run master commits

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