anchor.diff:  * align caption to match alignment of block image
   * make conum glyphs configurable in theme (use reference table to resolve)
   * CJK and/or multilingual support (see https://github.com/chloerei/asciidoctor-pdf-cjk)
  - ** document this in the README
   * description list term should keep together with content (file issue)
   * allow font properties to be set for lists (description_list, outline_list)
   * remove pdfmarks file after optimizing
  
positive.code: 
  * QUESTION should we show keys with hyphens instead of underscores in theming guide?
  
  * fix theming guide regarding table striping
  
  * part/chapter/section start pages are calculated twice, once for each running content; should be shared
   ** probably need to introduce a model object to hold the cache
  * UPSTREAM: highlighting of CSS w/ rouge seems messed up; don't recognize keywords
  
negative.code: * be more specific in theming guide as to where prose_margin_top and prose_margin_bottom apply
  * allow valign value to be a number (requires change to Prawn)
  * allow background color to be set for chapter / heading
  * allow border to be set around block image (#767)
  * file issue in prawn to dispatch to image handler for images it doesn't know about
  * add brief mention in theming guide that deeper customizations can be achieved by extending the converter
   ** see sandbox/asciidoctor_pdf_extensions.rb
  