Function for returning foldermap.map object to callback

@param {Function} callback function to call with result
@param {String|String[]} file string or object or array containing files to map
@param {Boolean} [created=false] Whether to mark objects as created
function _returnMap(callback, file, created){
  if(typeof file === 'string'){
    var map = foldermap.mapSync(file);
    Object.defineProperty(map, '_created', {value:created});
  } else {
    var map = {};
    for(var i in file){
      map[i] = foldermap.mapSync(file[i]);
      Object.defineProperty(map[i], '_created', {value:created});
    }
  }
  callback(null, map);
}