title: How do I left pad an NSString to fit it in a fixed width?
body: <p>I have NSString strings that represent times in HH:MM:SS but the HH and a digit of the MM may be omitted.</p>
  
  <p>I need to align columns of these values like this:</p>
  
  <pre><code>1:01:43
    43:23
     7:00
  </code></pre>
  
  <p>What's the easiest way to do this?</p>