language: node_js
node_js:
  - "6.1"
before_script:
  - npm install grunt-cli -g
script:
  - grunt

language: node_js
node_js:
  - "6"
before_script:
  - npm install grunt-cli -g
script:
  - grunt

Use latest node 6.x version on Travis CI
Use latest node 6.x version on Travis CI

According to the Travis docs [1], "6" can be used as a shortcut for
"latest 6.x release".

[1] https://docs.travis-ci.com/user/languages/javascript-with-nodejs#Available-Versions

Change-Id: Ib6a276298319b2865bc6ab8d05f9cdfc5d48264f
