language: node_js
node_js:
  - "8"
  - "7"
  - "6"
install:
  - yarn
script:
  - yarn run ci

language: node_js
node_js:
  - 6
  - 7
  - 8
  - 9
  - stable
install:
  - yarn
script:
  - yarn run ci

Add stable and 9 release of Node.js to CI config.
Add stable and 9 release of Node.js to CI config.
