Fixing travis config from last commit

.travis.yml

@@ -4,9 +4,9 @@ go:
   - 1.8
   - tip
 before_install:
-  - sudo add-apt-repository ppa:ubuntu-toolchain-r/test
+  - sudo add-apt-repository -y ppa:ubuntu-toolchain-r/test
   - sudo apt-get update
-  - sudo apt-get install libstdc++6
+  - sudo apt-get install -y libstdc++6
   - go get github.com/mattn/goveralls
   - ./contrib/grab-headless_shell.sh $HOME/hs
 script: