anchor.diff:  * document how the treetop parser is rebuilt
   * rewrite optimize-pdf using rghost
     - add Optimizer class; wire to cli
  +* use ImageMagick to uncompress PNG images before reading them (could also just document this)
   * rework font so we can set actual height, calculate x_height internally (use 1em for spacings)
   * padding top and bottom on content affects height_of calculations (need to review)
   * enable fallback font (Golo guide has problem with License block)
  
positive.code: * do we still need the converter hack in convert_content_for_block? (seems to be needed for admonitions)
  * avoid getting an empty last page (example: colist at bottom of page can cause this)
  * utility to coerce the color value transparent to nil (better handling in general)
  * cjk and/or multilingual support
  * description list term should keep together with content (file issue)
  * GhostScript Tiger SVG is reporting incorrect height when embedded (too much spacing below); bug in prawn-svg?
  * hardbreak in table cell results in extra endline (likely not normalizing cell content)
  
negative.code: = WORKLOG
  
  * use Groovy language specification as case study to find corner cases
    - perhaps progit2 as well; others?
  
  == TODO
  
  * create utility method to get % offset of page as y value (option to constrain to bounds)
  
  * **allow theme_font to set line_height** (honor this setting from document)
    - theme setting for code line height (currently using base_line_height)
  * implement convert_inline_indexterm (as noop; just to silence the warning)
  * use docdate attribute to set modification date on document (file issue)
  * more theme control over toc (font size, style, color per level)
  * prevent title-logo-image from spilling to next page (same with title content)
  * support font family and style for heading level
  * remove .to_s calls on color values now that theme normalizes them (perhaps should be a post-load theme procedure)
    - do CMYK values work for colors? no, but we should support an array value
  * split prawn_ext/extensions.rb into individual modules and include them
  * code cleanups (regexps to constants, nil? checks and such)
    - extract regex in ThemeLoader into constant
  * theme keys should be flatted to arbitrary depth
  * enable line above (or below?) title on title page (file issue)
  * quote all color values in reference themes
  * allow pdf-page-layout (portrait || landscape) to be set in document
  * attribute or role to control table shading (all, even, odd) (or call it striped like bootstrap?)
  * make conum glyphs configurable in theme (use reference table to resolve)
  