Fix pygments block matching

[mhils]

This PR is a fix for mitmproxy/pdoc#421. Consider the following Markdown:

# Section 1

```python
x = 1
```

# Section 2

<div>
test
</div>

markdown2 would previously first convert the fenced code block to <div class="codehilite">...</div>, and then, in _hash_html_blocks, match from the first pygments <div class="codehilite"> to the final </div> at the end of the file¹. Everything in between (such as # Section 2) would be skipped.

I also considered to directly hash the pygments output instead (mhils@9622c05), but that changes <p> paragraph wrapping and would be more of a breaking change. So I think this approach is preferrable.

Footnotes

1. _strict_tag_block_re does this before _liberal_tag_block_re matches. ↩

[nicholasserra]

The tests that were modified, they're all just html formatting changes right? Wanna make sure I didn't miss anything.

[mhils]

Yes, correct! :)

[mhils]

I've rebased this onto master and also added a fix for mitmproxy/pdoc#429, which depends on the formatting changes here. 😃

[nicholasserra]

LGTM thank you for the work on this