title: transformedValueClass to return Array of type AnyObject
body: <p>I'm trying to implement <code>NSValueTransformer</code> class named <code>ArrayValueTransformer</code> which is meant to transform an Array which can contain any type of object in it as follows:</p>
  
  <pre><code>class ArrayValueTransformer : NSValueTransformer {
      override class func transformedValueClass() -&gt; AnyClass {
          return Array&lt;AnyObject&gt;.self
      }
  }
  </code></pre>
  
  <p>But the return statement gives this error:</p>
  
  <pre><code>Type 'Array&lt;AnyObject&gt;' does not conform to protocol 'AnyObject'
  </code></pre>