Add better npm script documentation

[gvn]

EG:

  "scripts": {
    "lint": "eslint server.js js/cms.js"
  },
  "eslintConfig": {
    "extends": "./node_modules/mofo-style/.eslintrc.yaml",
    "env": {
      "browser": true,
      "node": true
    },
    "rules": {
      "no-console": 0
    }
  }

Point out gotcha that eslintConfig won't override the YAML config if you specify the YAML config as a flag on the CLI.