This is actually needed because Rouge will yield a `pre` tag with a `class` attribute anyway (even if we specify an empty string as the CSS class ; see [here](https://github.com/jayferd/rouge/blob/master/lib/rouge/formatters/html.rb#L42)). As you can see, the only way to avoid this is to set the `wrap` option to `false` when initializing the new `Formatter` but if do so, we can't rely on the Redcarpet plugin which makes the code a lot clearer I think.

Let me know if you prefer not to rely on this plugin and avoid this regex change ; I will update accordingly.