title: include dictionary or array value in swift string with backslash notation
body: <p>I'm testing out the playground for swift reading the ebook and am testing the backslash insert value into string thing..
  wondering how I could do this with a dictionnary array, but it does not seem to like it.</p>
  
  <pre><code>var str="dictionary values are \(dict['mine'])"
  </code></pre>
  
  <p>this errors out.
  just wondering what the correct way to escape this would be, or should I just concatenate them in this case.</p>