     public init(capacity: Int) {
         initialCapacity = capacity
         
-        version = 0
         _count = 0
         pushNextIndex = 0
      

    - parameter element: Element to enqueue.
    */
    public mutating func enqueue(element: T) {
        version++
        
        if count == storage.count {
            resizeTo(max(storage.count, 1) * resizeFactor)
        }

    
    private mutating func dequeueElementOnly() -> T {
        precondition(count > 0)
        
        let index = dequeueIndex
        let value = storage[index]!
