Wait function for reading files async.

wait_list

function wait(count, callback) {
  return function() {
    if (--count === 0) {
      callback();
    }
  }
}

var list_of_files = ['a', 'b', 'c'];
var report = wait(list_of_files.length, function() {
   console.log("done with them all");
});
list_of_files.eachAsync(function (file_data) {
  console.log('this file\'s data is', file_data);
  report();
});