fix(1.8): go 1.8 fix (#237)

* add support for 1.8

Author: msohailhussain

.travis.yml

@@ -45,6 +45,7 @@ jobs:
         - go get -v -d ./...
         # This pkg not in go 1.8
         - go get github.com/stretchr/testify
+        - pushd $GOPATH/src/github.com/stretchr/testify && git checkout v1.4.0 && popd
         # -coverprofile was not introduced in 1.8
         - make test