title: Setting an accessibility label on a UITabBarItem with no title
body: <p>I have a UITabBarItem like so:</p>
  
  <pre><code>_Controller.tabBarItem = [[UITabBarItem alloc] initWithTitle:nil image:nil tag:0];
  </code></pre>
  
  <p>But having nil for a title removes the label needed for accessibility and KIF testing. An alternative I found is to set the title and move it off the screen, but that seems like a hacky solution:</p>
  
  <pre><code>_Controller.tabBarItem.title = @"Foo";
  _Controller.tabBarItem.titlePositionAdjustment = UIOffsetMake(0, 200);
  </code></pre>
  
  <p>Is it possible to have a UITabBarItem without a title, but still have an accessibility label?</p>
  
  <p>EDIT to add full code for tab bar and background button code:</p>
  
  <pre><code>- (void) loadViewController {
      _Controller = [[UIViewController alloc] init];
      UIImage *normalImage = [UIImage imageNamed:@"bar.png"];
      UIImage *selectedTabImage = [UIImage imageNamed:@"barHover.png"];
      [self addCenterButtonWithImage:normalImage
                      highlightImage:selectedTabImage];
  
      _Controller.tabBarItem = [[UITabBarItem alloc] initWithTitle:nil image:nil tag:0];
  }
  
  // Create a custom UIButton and add it to the center of our tab bar
  -(void) addCenterButtonWithImage:(UIImage*)buttonImage highlightImage:(UIImage*)highlightImage
  {
      UIButton* button = [UIButton buttonWithType:UIButtonTypeCustom];
      button.frame = CGRectMake(0.0, 0.0, buttonImage.size.width, buttonImage.size.height);
      [button setBackgroundImage:buttonImage forState:UIControlStateNormal];
      [button setBackgroundImage:highlightImage forState:UIControlStateHighlighted];
      [button addTarget:self action:@selector(openCamera) forControlEvents:UIControlEventTouchUpInside];
  
      button.center = CGPointMake(self.tabBar.frame.size.width/2.0, self.tabBar.frame.size.height/2.0 - 6.0);
  
      [self.tabBar addSubview:button];
  }
  </code></pre>