anchor.diff:    
     argParser.addOption('key', abbr: 'k',
         help: 'google api key', 
  -      defaultsTo: null);
  +      defaultsTo: '');
     
     argParser.addOption('url', abbr: 'u',
         help: 'url',
         defaultsTo: "http://www.google.com");
     
  -  /* these are exclusive */
     argParser.addOption('type', abbr: 't',
         allowed: [UrlShortener.SHORTEN, UrlShortener.EXPAND, UrlShortener.ANALYTICS],
         help: "type of action to execute",
  
positive.code:   var type = args['type'];
    
    UrlShortener urlShortener = new UrlShortener(url: url,
        command: type,
        key: key,
        curlPath: curl);
    Future f = urlShortener.execute();
    f.handleException((error) {
      print("error: $error");
  
negative.code:     Directory directory = new Directory.current();
      processOptions.workingDirectory = directory.path;
      processOptions.environment = new Map();
      print("$curlPath $processArgs");
      Process.run(curlPath, processArgs, processOptions)
      ..handleException((error) {
        print("Error: $error");
  