changed travis to support ncclient install from github for python 3
changed travis to support ncclient install from github for python 3

pklimai/py-junos-eznc,spidercensus/py-junos-eznc,pklimai/py-junos-eznc,spidercensus/py-junos-eznc,pklimai/py-junos-eznc,Juniper/py-junos-eznc,spidercensus/py-junos-eznc,Juniper/py-junos-eznc,Juniper/py-junos-eznc