[NPM] Run npm scripts in series

After creating several npm script it becomes useful to run multiple scripts back-to-back in series. This is a nice feature because you can enforce that one script needs to complete before starting another one.

  "scripts": {
    "start": "node index.js",
    "test": "npm run eslint && npm run stylelint && mocha spec/ --require babel-register",
    "eslint": "eslint --cache --fix ./",
    "stylelint": "stylelint ‘**/*.scss‘ --syntax scss",
    "stylelint:fix": "stylefmt -R src/"
  },