title: stringByAppendingPathComponent is unavailable
body: <p>My app shares photo on Instagram, to do this it first saves it on a temporary directory:</p>
  
  <pre><code>let writePath = NSTemporaryDirectory().stringByAppendingPathComponent("instagram.igo")
  </code></pre>
  
  <p>It was working on <code>Swift 1.2</code>, but does not work on <code>Swift 2.0</code>.</p>
  
  <p>Given error message is: </p>
  
  <blockquote>
    <p>stringByAppendingPathComponent is unavailable: use URLByAppendingPathComponent on NSURL instead.</p>
  </blockquote>