title: NSString issues
body: <p>I have an NSString that gets assigned a string value.  How do I take this <code>NSString</code> and insert <code>@"-thumbnail"</code> between the file's name and its extension?</p>
  
  <p>In other words, how do I go from:</p>
  
  <pre><code>NSString *fileName = @"myFile.png";
  </code></pre>
  
  <p>to:</p>
  
  <pre><code>NSString *thumbnailName = [NSString someMagicFunction...]
  NSLog(@"%@", thumbnailName);  // Should Output "myFile-thumbnail.png"
  </code></pre>