code: function findConfig_p(appDir){
    var filePath = path.join(appDir, ".shiny_app.conf");
    return fsutil.safeStat_p(filePath)
    .then(function(stat){
      if (stat && stat.isFile()){
        return (filePath);
      }
      throw new Error('Invalid app configuration file.');
    });
  }
docs: Check to see if there's a configuration file in the given app directory,
  if so, parse it.
  @param appDir The base directory in which the application is hosted.
  @return A promise resolving to the path of the application-specific
  configuration file