title: Center NSTextAttachment image next to single line UILabel
body: <p>I'd like to append an <code>NSTextAttachment</code> image to my attributed string and have it centered vertically.</p>
  
  <p>I've used the following code to create my string:</p>
  
  <pre><code>NSMutableAttributedString *str = [[NSMutableAttributedString alloc] initWithString:DDLocalizedString(@"title.upcomingHotspots") attributes:attrs];
  NSTextAttachment *attachment = [[NSTextAttachment alloc] init];
  attachment.image = [[UIImage imageNamed:@"help.png"] imageScaledToFitSize:CGSizeMake(14.f, 14.f)];
  cell.textLabel.attributedText = [str copy];
  </code></pre>
  
  <p>However, the image appears to align to the top of the cell's <code>textLabel</code>.</p>
  
  <p><a href="https://i.stack.imgur.com/ilpEl.png" rel="noreferrer"><img src="https://i.stack.imgur.com/ilpEl.png" alt="text attachment offset problem screenshot"></a></p>
  
  <p>How can I change the rect in which the attachment is drawn?</p>