XRENDERING-297: Upgrade to PegDown 1.4.0
XRENDERING-297: Move all specific tests for Markdown to the proper subfolder
XRENDERING-297: Add superscript syntax to Markdown
XRENDERING-297: Add subscript syntax to Markdown
XRENDERING-297: Add block (XWiki) macro syntax to Markdown
XRENDERING-297: Add inline macro syntax to Markdown
XRENDERING-297: Code-style fixes and some minor changes in Markdown
XRENDERING-297: Preserve parameters order in macros