title: changing the MFMailComposeViewController navigationBar title font
body: <p>I have a <code>MFMailComposeViewController</code> and when I've set the subject it also sets it as the subject.
  The question is how do I customize the font of the title and color?</p>
  
  <pre><code>MFMailComposeViewController *picker = [[MFMailComposeViewController alloc] init];
  [picker setSubject:@"Feedback for MyApp"];
  </code></pre>