title: How does NSJSONSerializer determine the encoding of the given data?
body: <p>I'm using NSJSONSerializer to parse some json formatted data. The data contains some 'ü' and 'ö' and such. 
  I find that it does return nil, when not beforehand converting the NSData to a NSString with NSASCIIStringEncoding and reconverting it back to NSData, so that 'ü' is converted to u and so on. 
  The original format of the Data is ISO-8859-1.
  How ca i possibly advise the json parser to use this encoding?</p>