travis: test against go 1.9

.travis.yml

@@ -3,6 +3,7 @@ go:
     - 1.6.x
     - 1.7.x
     - 1.8.x
+    - 1.9.x
 sudo: false
 install:
     - go get -v github.com/alecthomas/gometalinter
@@ -18,7 +19,7 @@ script:
       --enable=unconvert
       --deadline=4m ./spew | tee /dev/stderr)"
     - go test -v -race -tags safe ./spew
-    - go test -v -race -tags testcgo ./spew -covermode=count -coverprofile=profile.cov
+    - go test -v -race -tags testcgo ./spew -covermode=atomic -coverprofile=profile.cov
 after_success:
     - go get -v github.com/mattn/goveralls
     - goveralls -coverprofile=profile.cov -service=travis-ci