anchor.diff:  * HIGH: review the table border color
   * HIGH: style example block
   * HIGH: allow theme to be customized using stylesheet attribute
  +* MEDIUM: headshot has too much top margin when at top of page (not below section title)
   * MEDIUM: add landmarks nav list to nav.xhtml
   * support both jpg and png avatars
   * add docinfo support
  
positive.code: * HIGH: add back cover if specified
  * MEDIUM: set modified date explicitly
  * MEDIUM: use function to build and manipulate image paths
  * support subtitle as separate from main title in package metadata
  * support collection title in package metadata
  
  
negative.code: * recreate ellipses in M+ 1p to be on baseline
  
  .Stylesheet
  * CRITICAL: padding around code in formal listing blocks
  * CRITICAL: check style of level 5 and 6 headings (see Groovy docs)
  * CRITICAL: use CSS3 filter scheme that allows admonitions to appear correctly on Google Play Books
    - see if Google Play books supports JavaScript and epubReadingSystem (no, but adds its own class to body)
  