wrong order of parsing underscores and Grave accent in tricky text

[Peter Molnar]

This is an edge-case situation but the result in fine in Parsedown, fails in Extra.

My extra setup:

        $parsedown = new ParsedownExtra();
        $parsedown->setBreaksEnabled(true);
        $parsedown->setUrlsLinked(true);
        $md = $parsedown->text ( $md );

example text:

  - and the post content preg_match `"/(?:www\.)?youtube\.com\/watch\?v=[a-zA-Z0-9_-]+/"`
  the type is `video`

Result is as expected ( preformatted between the apostrophes, no em results ) in Parsedown, however, Extra interprets the text between the underscores as em text first and the type is becomes preformatted.

Reproduceable with http://parsedown.org/demo.