add 'service' goveralls flag
diff --git a/.travis.yml b/.travis.yml
index b9f7707..7045e0e 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -15,4 +15,4 @@
   - if ! go get github.com/golang/tools/cmd/cover; then go get golang.org/x/tools/cmd/cover; fi
 script:
   - script/cibuild
-  - $HOME/gopath/bin/goveralls
+  - $HOME/gopath/bin/goveralls -service=travis-ci