language: node_js
node_js:
  - stable
  - 8
  - 6
  - 4
script:
  - npm test

language: node_js
node_js:
  - stable
  - 12
  - 10
  - 8
script:
  - npm test

Update node versions, drop v4/v6, add v10/v12
ci: Update node versions, drop v4/v6, add v10/v12
