Remove debug print

Merge pull request yuin#205 from brief/fix-footnote-backlinks

Keep backlinks with footnote text

Fixes a bug related to escaped pipes in a table cell

refactoring

Fixes yuin#176

Closes yuin#161

- Implement footnote configurations defined in original markdown extra.
- Add OwnerDocument() method to ast.Node
- Add Meta() method to *ast.Document

Fixes yuin#148

Fixes yuin#78

Merge pull request yuin#139 from yaaax/patch-1

Fix typo

Improve typographer