commonmark-java 0.8.0

Update to CommonMark spec 0.27 (#73):

• Treat h2..h6 as HTML blocks well
• Allow shortcut reference link before open parenthesis (if parenthesis is not part of a valid inline link)

API changes:

• AttributeProvider.setAttributes now has an additional tagName argument and is called for all HTML tags of a block. This allows users to add attributes for the pre tag of a code block in addition to code. Also added attribute provider support for additional HTML tags, namely em, strong, code and br. (#74)

ext-autolink:

• Bump version of autolink-java dependency (no changes affecting extension)

ext-heading-anchor:

• Fix IllegalArgumentException on Android (#71)