Enable eslint caching in development (#1578)

* Enable eslint caching in development

POC for #740. Haven't found any problem, build times improved about 1s on my project and machine.

* Bump eslint-loader to 1.6.3

* move @remove-on-eject block to persist cache config on eject

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

@@ -114,13 +114,14 @@ module.exports = {
         test: /\.(js|jsx)$/,
         enforce: 'pre',
         use: [{
-          // @remove-on-eject-begin
-          // Point ESLint to our predefined config.
           options: {
+            // @remove-on-eject-begin
+            // Point ESLint to our predefined config.
             configFile: path.join(__dirname, '../.eslintrc'),
-            useEslintrc: false
+            useEslintrc: false,
+            // @remove-on-eject-end
+            cache: true
           },
-          // @remove-on-eject-end
           loader: 'eslint-loader'
         }],
         include: paths.appSrc