update .travis.yml

.travis.yml

@@ -1,8 +1,10 @@
 language: go
 go:
   - tip
+sudo: false
+
 before_install:
   - go get github.com/mattn/goveralls
   - go get golang.org/x/tools/cmd/cover
 script:
-    - $HOME/gopath/bin/goveralls -repotoken 3gHdORO5k5ziZcWMBxnd9LrMZaJs8m9x5
+  - $HOME/gopath/bin/goveralls -repotoken 3gHdORO5k5ziZcWMBxnd9LrMZaJs8m9x5