title: Error using += to append a Character to a String: String is not identical to UInt8
body: <p>When trying to use the <code>+=</code> operator to append a <code>Character</code> to a <code>String</code>, I'm getting the following error:</p>
  
  <blockquote>
    <p>String is not identical to UInt8</p>
  </blockquote>
  
  <p>The error occurs on the <code>puzzleOutput += char</code> line in the code below:</p>
  
  <pre><code>let puzzleInput = "great minds think alike "
  var puzzleOutput = ""
  
  for char in puzzleInput
  {
      switch char
      {
      case "a","e","i","o","u":
          continue
  
      default:
         puzzleOutput += char
      }
  }
  
  println(puzzleOutput)
  </code></pre>
  
  <p>How can I append a <code>Charater</code> to a <code>String</code>?</p>