Two new optional parameters in StealthResponse.markdown()

markdown() now has two optional parameters!

1. content_xpath An XPath expression, in the form of a string, which can be used to narrow down what text is converted to Markdown. This can be useful if you don't want the header and footer of a webpage to be turned into Markdown.
2. ignore_links A boolean value that tells Html2Text whether it should include any links in the output of the Markdown.