Finalize version 1.0.0

[pbodnar]

These should be the final changes before releasing the next version of mistletoe - this time we should feel already confident enough to name it 1.0.0.

And this a preview of the release notes:

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WARNING - Backwards compatibility changes:

• Contrib folder update #167: For practical reasons and for following common packaging practices, contrib folder got moved under the mistletoe folder / package. So if you reference a renderer from that folder, you need to reference it as mistletoe.contrib.<renderer> now.
• See "change handling of (white)space characters in code spans" below. We keep processing extra whitespace characters at the parsing level, so that all renderers can benefit from it out-of-the-box. Provided that a custom renderer, for whatever reason, relied on all the spaces being collapsed, it needs to do that collapsing itself now (e.g. ' '.join(re.split('[ \n]+', content.strip())), or re.sub('[ \n]+', ' ', content.strip())).

Added:

• JIRARenderer: Support link title notation, i.e. [label](url "title") gets transformed to [label|url|title] (💡 implement link titles in the JIRARenderer (contrib) #161)

Fixed:

• Make the traverse() function actually work with various input parameters:
  • filtering by class (fix: Make filtering children by class in traverse() actually work #157, fix: Apply traverse class filter to source when include_source=True #158)
  • filtering by depth (fix: Make limiting depth in traverse() actually work #159)
• Compatibility with the latest CommonMark specification v0.30 (Update to CommonMark v0.30 #108):
  • Change handling of (white)space characters in code spans (Fix for part of #108, Update to CommonMark v0.30 #156; in line with Don't collapse interior spaces in code spans commonmark/commonmark-spec#532 and Codespan containing single space. commonmark/commonmark-spec#569)
  • Fix handling of tabs and parsing continuation lines within list items (List Items separated by tab character not parsed correctly #89 via Fix for #89, List Items separated by tab character not parsed correctly. #164)
  • Fix the other examples, mostly edge cases, from the spec (see Fix for #108, CommonMark 0.30 spec compliance, part 2 #165 and Fix for #108, CommonMark 0.30 spec compliance, part 3 #168 for details; IndexError on malformed markdown tables #173 seems to be fixed as well)
• Make parsing of link reference definitions (a.k.a. Footnotes) more strict - spec compliant (Blocks in between footlink definitions are skipped when parsing #132)
• Fix handling of special punctuation characters when parsing emphasis (Italics parsing broken when underscore is followed by some characters #96, Emphasis around link ignored when followed by a special punctuation character #175)

Updated:

• Smaller inner working refactorings, like Merge block_token._root_node and span_token._root_node into a single object #171.

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[pbodnar]

@anderskaplan or other great contributors, here's an opportunity to give some final feedback before I release and publish mistletoe 1.0.0 in a few days. I hope I have prepared all well, yet I could have overlooked something. So thanks in advance for your prospective review. :)

[pbodnar]

PS: For future releases, I plan to use the GitHub's Milestones feature, so that it is more visible, even in advance, which issue or pull request goes to which version.

[anderskaplan]

Looks good to me!