title: setting the text color of UIBarButtonItem by appearance proxy
body: <p>Here's what is being set and it's close to the color I need:</p>
  
  <pre><code>NSDictionary *barButtonItemTitleAttributesEnabled = @{
                                                 NSFontAttributeName:[UIFont MRFontLightOfSize:17],
                                                 NSForegroundColorAttributeName:[UIColor whiteColor]
                                                 };
  NSDictionary *barButtonItemTitleAttributesDisabled = @{
                                                        NSFontAttributeName:[UIFont MRFontLightOfSize:17],
                                                        NSForegroundColorAttributeName:[UIColor colorWithWhite:1.0f alpha:0.25f]
                                                        };
  
  [[UIBarButtonItem appearance] setTitleTextAttributes:barButtonItemTitleAttributesEnabled forState:UIControlStateNormal];
  [[UIBarButtonItem appearance] setTitleTextAttributes:barButtonItemTitleAttributesDisabled forState:UIControlStateDisabled];
  </code></pre>
  
  <p>But I'd prefer to somehow set the disabled text color to the same color as the selected state, is there a way to do that with the appearance proxy calls?</p>
  
  <p>Also tried this:</p>
  
  <pre><code>NSDictionary *barButtonItemDisabled = [[UIBarButtonItem appearance] titleTextAttributesForState:UIControlStateSelected];
  [[UIBarButtonItem appearance] setTitleTextAttributes:barButtonItemTitleAttributesEnabled forState:UIControlStateNormal];
  [[UIBarButtonItem appearance] setTitleTextAttributes:barButtonItemDisabled forState:UIControlStateDisabled];
  </code></pre>