function isNode(object) {
  return !!(object && (
    typeof Node === 'function' ? object instanceof Node :
      typeof object === 'object' &&
      typeof object.nodeType === 'number' &&
      typeof object.nodeName === 'string'
  ));
}
Combines multiple className strings into one.
http://jsperf.com/joinclasses-args-vs-array

@param {...?string} classes
@return {string}