remove Travis caching to get around npm ls issue
remove Travis caching to get around npm ls issue

rgbkrk/nteract,captainsafia/nteract,rgbkrk/nteract,nteract/composition,nteract/nteract,nteract/nteract,jdetle/nteract,nteract/composition,jdetle/nteract,temogen/nteract,nteract/nteract,temogen/nteract,jdfreder/nteract,captainsafia/nteract,rgbkrk/nteract,jdfreder/nteract,rgbkrk/nteract,nteract/composition,rgbkrk/nteract,nteract/nteract,nteract/nteract,jdetle/nteract,temogen/nteract,jdfreder/nteract,jdfreder/nteract,captainsafia/nteract,jdetle/nteract,captainsafia/nteract