language: node_js
node_js:
  - "9"
  - "8"
  - "6"
before_script:
  - npm i -g typings
  - typings install
script:
  - npm run ci
language: node_js
node_js:
  - "9"
  - "8"
  - "6"
before_script:
  - npm i -g yarn
script:
  - yarn ci

Install yarn on Travis at begin of CI job
Install yarn on Travis at begin of CI job