title: NSString converting percentage characters
body: <p>I have an NSString *str = @"T%B3%C3%83";</p>
  
  <p>where %C3 represents A with an umlut (I think), %B3 an m, %83 a superscript 3...</p>
  
  <p>What is the best way to convert these percentages into the actual characters.</p>
  
  <p>Thanks.</p>