Markdown2

- [pull 590] Fix underscores within bold text getting emphasized (589)
- [pull 591] Add Alerts extra
- [pull 595] Fix img alt text being processed as markdown (594)
- [pull 598] Add `link-shortrefs` extra (597)
- [pull 600] Use urandom for SECRET_SALT
- [pull 602] Fix XSS issue in safe mode (601)
- [pull 604] Fix XSS injection in image URLs (603)

- [pull 519] Add support for custom extras
- [pull 519] Drop Python 3.5 support
- [pull 568] Add `prepend` arg to toc extra (397)
- [pull 569] Process HTML comments as markdown in 'escape' safe mode
- [pull 570] Fix syntax warnings in test suite
- [pull 572] Process inline tags as HTML blocks when they span multiple lines (571)
- [pull 573] Add new LaTeX Extra
- [pull 576] Fix `html`, `head` and `body` tags being wrapped in `<p>` tags (575)
- [pull 578] Graceful handling of broken lists when cuddled-lists extra is enabled
- [pull 581] Add type hints (562)
- [pull 581] Drop Python 3.6 and 3.7 support
- [pull 582] Fix fenced code blocks breaking lists (580)
- [pull 586] Fix 583 by tweaking incomplete tag regex
- [pull 587] Fix AssertionError on malformed HTML (584)

- [pull 559] Allow cuddled tables (557)
- [pull 560] Fix `markdown-in-html` not always splitting HTML tags into separate lines (558)
- [pull 564] Fix incomplete comments in safe mode not being escaped (563)
- [pull 566] Fix crash in `markdown-in-html` extra (565)

- [pull 547] Update `markdown-in-html` extra to handle markdown on same line as HTML (546)
- [pull 550] Fix tables with trailing whitespace not being recognized (549)
- [pull 545] Fix multiple instances of strong emphasis (`**`) in one line (541)
- [pull 556] Fix incorrect parsing of links after square brackets (552)

- [pull 524] Fix angles being escaped in style blocks (issue 523)
- [pull 527] Fix base64 images being corrupted in safe mode (issue 526)
- [pull 529] Add `breaks` extra with ability to hard break on backslashes (issue 525)
- [pull 532] Fix 493 persisting when `code-friendly` extra enabled
- [pull 535] Update `_slugify` to use utf-8 encoding (issue 534)
- [pull 536] Maintain order of appearance in footnotes
- [pull 538] Include HTML headers in TOC
- [pull 540] Add mechanism to prevent header ID counter resetting (issue 530)

- [pull 520] Allow more relative links in safe mode (issue 517)
- [pull 521] Always restore hashed HTML blocks (issue 185)
- [pull 522] Add `middle-word-em` extra