ESLint 4 (#2735)

* Update eslint-loader 1.7.1 -> 1.9.0

* Add eslintPath option

* Update eslint 3.19.0 -> 4.1.1

* Update peer dependencies

* Move eslintPath config to outside @remove-on-eject

packages/react-scripts/config/webpack.config.dev.js

@@ -136,6 +136,7 @@ module.exports = {
           {
             options: {
               formatter: eslintFormatter,
+              eslintPath: require.resolve('eslint'),
               // @remove-on-eject-begin
               baseConfig: {
                 extends: [require.resolve('eslint-config-react-app')],