Install babel-eslint as dev-dependency about babel-eslint

[Cellule]

Mostly, it depends on how you run ESlint.
If it is launched from the command line with $ eslint src then it will use the one installed globally, which will in turn need the parser to be installed globally.
If you have both eslint and babel-eslint installed locally then you can make a npm script like

{
  "scripts": { "lint": "eslint src" }
}

and then run $ npm run lint
This will use the local version of eslint and also it will look locally for your parser.

[sebmck]

the README instructs to install globally - why?

Because most people use eslint via the CLI and it's the easiest way to guarantee that it will work.