title: Must call a designated initializer of the superclass 'UIViewController'
body: <p>I have a class A defined in ObjC and Class B - subclass of A defined in Swift. 
  The implementation is as follows:</p>
  
  <p><em>Class A</em></p>
  
  <pre><code>- (id)init {
       return [super init];
  }
  </code></pre>
  
  <p><em>Class B</em></p>
  
  <pre><code>init(url: NSURL) {
      super.init()
      let request = NSMutableURLRequest(URL: url)
      request.setValue(valueID, forHTTPHeaderField: "value_ID")
      urlRequest = request
  }
  
  convenience init(recoveryURL: NSURL) {
      self.init(url: recoveryURL)
  }
  
  required public init?(coder aDecoder: NSCoder) {
      fatalError("init(coder:) has not been implemented")
  }
  </code></pre>
  
  <p>Class B is initialized as follows (since its loaded from the xib file):</p>
  
  <pre><code>ClassB *b = [[ClassB alloc] initWithNibName:@"ClassA" bundle:nil];
  </code></pre>
  
  <p>The error is seen on <code>super.init()</code> line inside <code>init(url: NSURL)</code> of class B. I'm trying to use convenience initializers. I would appreciate if someone can point me @ where am I going wrong? </p>