function tag (name, attrs, close, content) {
  var end = close ? '/>' : '>';
  var pairs = [];
  var tag;

  for (var key in attrs) {
    if (Object.prototype.hasOwnProperty.call(attrs, key)) {
      pairs.push(key + '="' + escape(attrs[key]) + '"');
    }
  }

  tag = '<' + name + (pairs.length ? ' ' + pairs.join(' ') : '') + end;
  if (content) {
    tag += content + '</' + name + end;
  }
  return tag;
}
HTML tag helper.

@param name
@param attrs
@param close
@param content
@return {string}