code: function async(callback)
  {
    var isAsync = false;
  
    // check if async happened
    defer(function() { isAsync = true; });
  
    return function async_callback(err, result)
    {
      if (isAsync)
      {
        callback(err, result);
      }
      else
      {
        defer(function nextTick_callback()
        {
          callback(err, result);
        });
      }
    };
  }
docs: Runs provided callback asynchronously
  even if callback itself is not
  
  @param   {function} callback - callback to invoke
  @returns {function} - augmented callback