title: WKWebView: How to local storage enable in iOS8
body: <p>I'm trying to local storage enable.
  But in iOS8, I can't find how to do it. </p>
  
  <pre><code>let configuration = WKWebViewConfiguration()
  
  if #available(iOS 9.0, *) {
      configuration.websiteDataStore = WKWebsiteDataStore.defaultDataStore()
  } else {
      //??
  }
  </code></pre>