run tests on go version: 1.6, 1.7, 1.8 and tip (#50)
run tests on go version: 1.6, 1.7, 1.8 and tip (#50)

* run tests on go version: 1.6, 1.7, 1.8 and tip

* remove tip version

* added go tip version and allow failures

nuveo/gofn,nuveo/gofn,nuveo/gofn