// usage
class MyViewController: UIViewController {
  required init(coder aDecoder: NSCoder) {
    super.init(coder: aDecoder)
    setupTabBarItem("entries")
  }
}

// where "entries" is the name of the image.
// should have 2 images named tabbar-entries and tabbar-entries-selected

extension UIViewController {

  func setupTabBarItem(imageName: String) {
    var selectedImage = UIImage(named: "tabbar-\(imageName)-selected")
    selectedImage = selectedImage?.imageWithRenderingMode(.AlwaysOriginal)
    var image = UIImage(named: "tabbar-\(imageName)")
    image = image?.imageWithRenderingMode(.AlwaysOriginal)
    tabBarItem = UITabBarItem(title: nil, image: nil, tag: 0)
    tabBarItem.image = image
    tabBarItem.selectedImage = selectedImage
    tabBarItem.imageInsets = UIEdgeInsets(top: 6, left: 0, bottom: -6, right: 0) // insets are optional
    tabBarController?.tabBar.tintColor = UIColor.grayColor()
  }

}