Merge pull request #1 from oreillymedia/sanders

:+1:  Fixed well-formedness error in layout.html
Update layout.html

Changing doctype
Update layout.html
changing layout variables into correct liquid format
Merge pull request #2 from oreillymedia/layout_fixes

changing layout variables into correct liquid format
fixing head
No need to reference ah-default directly in stylesheet, as the PDFWorker takes care of this.