Markdown-sensible characters processing

This test checks special characters processing inside URLs: parenthesis and brackets should be escaped to keep markdown image and anchor syntax safe and sound.

• Some MSDN link using parenthesis
• Google search result URL with unescaped brackets
• Yet another test for [brackets], {curly braces} and (parenthesis) processing inside the anchor
• Use automatic links like http://example.com/ when the URL is the label
• Exempt non-absolute_URIs from automatic link detection

And here are images with tricky attribute values: