function getAllVisitors(excludes) {
  var ret = [];
  for (var i = 0, il = transformRunOrder.length; i < il; i++) {
    if (!excludes || excludes.indexOf(transformRunOrder[i]) === -1) {
      ret = ret.concat(transformVisitors[transformRunOrder[i]]);
    }
  }
  return ret;
}
Given a list of transform names, return the ordered list of visitors to be
passed to the transform() function.

@param {array?} excludes
@return {array}