title: enum's rawValue property not recognized
body: <p>I'm using Xcode 6's playground to try out enums in Swift:  </p>
  
  <pre><code>enum Rank: String
  {
      case One = "One", Two="Two"
  
      init(rawValue : String)
      {
          self.rawValue = rawValue
      }
  }
  </code></pre>
  
  <p>I want to override init so that the enum can be initialized using it's rawValue as argument. But I get an error:  </p>
  
  <p><img src="https://i.stack.imgur.com/CYZof.png" alt="enter image description here"></p>
  
  <p>But according to the <a href="https://developer.apple.com/library/mac/documentation/Swift/Conceptual/Swift_Programming_Language/GuidedTour.html" rel="noreferrer">Apple's Swift guide</a> my code should be correct.</p>