message: Add some more docs to readme.
diff: # create-sumup-react-app
  +## Prerequisites
  +
  +## Steps to start a new project
  +
  +1. Run the following command, and pick the name of your project. It will create a new directory inside your current directory.
  +
  ```javascript
  curl -L https://raw.githubusercontent.com/sumup/create-sumup-react-app/master/create-sumup-react-app.sh | bash -s -- {project-name}
  ```
  +2. Edit `package.json` and amend the `test` script:
  +
  +```
  +"test": "react-app-rewired test --env=jsdom --transformIgnorePatterns \"node_modules/\\(?!\\(@sumup/circuit-ui\\)/\\)\"/g"
  +```
  +
  +This is temporary ;)
  +
  +3. Start your app with `yarn start`
  +
  ## Troubleshooting
  +### Engine node is incompatible
  ```
  error eslint@5.0.1: The engine "node" is incompatible with this module. Expected version "^6.14.0 || ^8.10.0 || >=9.10.0".
  error Found incompatible module
  ```
  Use a version of node that is compatible with ESLint. This is easy to accomplish with [nvm](https://github.com/creationix/nvm).
  +
  +### Error watching file for changes
  +```
  +2017-05-02 09:49 node[8980] (FSEvents.framework) FSEventStreamStart: register_with_server: ERROR: f2d_register_rpc() => (null) (-22)
  +2017-05-02 09:49 node[8980] (FSEvents.framework) FSEventStreamStart: register_with_server: ERROR: f2d_register_rpc() => (null) (-22)
  +2017-05-02 09:49 node[8980] (FSEvents.framework) FSEventStreamStart: register_with_server: ERROR: f2d_register_rpc() => (null) (-22)
  +events.js:163
  + throw er; // Unhandled 'error' event
  + ^
  +
  +Error: Error watching file for changes: EMFILE
  + at exports._errnoException (util.js:1050:11)
  + at FSEvent.FSWatcher._handle.onchange (fs.js:1376:11)
  +error Command failed with exit code 1.
  +```
  +
  +Make sure you have watchman installed.
  +
  +```
  +brew install watchman
  +```
  