anchor.diff:    - fix SVG to a single page (check height + caption height)
   * allow background color to be set for heading
   * allow border to be set around block image
  -
  +* switch wolpertinger to howling wolf mouse
  +* support arbitrary numeric entities (convert to unicode)
  +* add brief mention in theming guide that deeper customizations can be achieved by extending the converter
  +* allow alignment of list to be set separately from base align (and perhaps a hint in document)
  +
  +* *margin per heading level* (see https://github.com/asciidoctor/asciidoctor-pdf/issues/176)
  +* document how to override the Ruby code to get custom styling in the theming guide
  +* convenience method to check if there's enough room for another line on page
   * allow font size in theme to be specified in em or %
   * allow dynamic background image with page number in path
   * running header/footer covers content (perhaps just a limitation that needs to be documented)
  
positive.code: * https://code.google.com/p/origami-pdf/[Origami PDF: A PDF inspection library]
  * https://github.com/a1ee9b/PrintPretty[A theme for PDF designed for printing]
  * http://randomtextgenerator.com[Random Text Generator, supports multiple languages]
  
negative.code:   - separate running content for chapter page (by default uses normal content)
  * should we rename base_ to body_ to make it more familiar to CSS developers?
  * support !include in theme file (file issue)
  * add cover page example to chronicles so people see how to use it
  * don't orphan a single line of paragraph (send it with a buddy line)
  * implement stem support
  