code: function searchPodspecFilePath(currentDir, callback) {
      var cDir = currentDir || process.cwd();// default: cwd
      fs.readdir(cDir, function (err, files) {
          if (err) {
              return callback(err);
          }
          var results = files.filter(function (file) {
              return path.extname(file) === '.podspec';
          });
          // return first filePath
          if (results.length == 0) {
              callback(new Error("not found podspec file"));
          } else {
              var filePath = results.shift();
              callback(null, filePath);
          }
      });
  }
docs: find podspec and return find first file path
  @param currentDir
  @param callback