code: function(fn) {
  				funcGuard(fn);
  				if (completeQueue !== noop) {
  					throw new Error('queue `then` already set');
  				}
  				if (!err) {
  					completeQueue = fn;
  					if (!remaining) {
  						complete = true;
  						completeQueue(tasks);
  					}
  				}
  				return q;
  			}
docs: The callback to execute once all "deferred" functions have completed.  Will only be invoked once.
  @param  {Function} f The callback, receives an array of the return/callbacked
  values of each of the "deferred" functions