Update eslint-config-react-app version in the guide

packages/react-scripts/template/README.md

@@ -174,7 +174,7 @@ Then add this block to the `package.json` file of your project:
 Finally, you will need to install some packages *globally*:
 
 ```sh
-npm install -g eslint-config-react-app@0.2.1 eslint@3.8.1 babel-eslint@7.0.0 eslint-plugin-react@6.4.1 eslint-plugin-import@2.0.1 eslint-plugin-jsx-a11y@2.2.3 eslint-plugin-flowtype@2.21.0
+npm install -g eslint-config-react-app@0.3.0 eslint@3.8.1 babel-eslint@7.0.0 eslint-plugin-react@6.4.1 eslint-plugin-import@2.0.1 eslint-plugin-jsx-a11y@2.2.3 eslint-plugin-flowtype@2.21.0
 ```
 
 We recognize that this is suboptimal, but it is currently required due to the way we hide the ESLint dependency. The ESLint team is already [working on a solution to this](https://github.com/eslint/eslint/issues/3458) so this may become unnecessary in a couple of months.