TASK: Use latest node and yarn for travis

Author: Markus Günther

.travis.yml

@@ -4,6 +4,8 @@ cache:
   directories:
     - node_modules
 node_js:
-  - "4"
+  - "node"
 before_install:
-  - npm install -g babel-cli
+  - curl -o- -L https://yarnpkg.com/install.sh | bash -s -- --version v1.9.4
+  - export PATH="$HOME/.yarn/bin:$PATH"
+  - yarn global add babel-cli