language: node_js
node_js:
  - "6"
  - "4"

cache:
  directories:
    - node_modules

install:
  - npm install

language: node_js
node_js:
  - "10"
  - "8"
  - "6"

cache:
  directories:
    - node_modules

install:
  - npm install

Change to latest LTS node versions
Change to latest LTS node versions 

Kept 6 for the time being..