function replacementForNode (node) {
  var rule = this.rules.forNode(node);
  var content = process.call(this, node);
  var whitespace = node.flankingWhitespace;
  if (whitespace.leading || whitespace.trailing) content = content.trim();
  return (
    whitespace.leading +
    rule.replacement(content, node, this.options) +
    whitespace.trailing
  )
}
Converts an element node to its Markdown equivalent
@private
@param {HTMLElement} node The node to convert
@returns A Markdown representation of the node
@type String