anchor.diff:  * cache stateless cell data resolved from theme (don't need to recalc each time; at least per table)
   * FILE ISSUE: autowidth on table doesn't work for multi-line content (prawn-table bases width calculation on normalized value)
     - table ends up being stretched even though it doesn't need to be
  +  - I don't know a way to determine how much width a block of rendered content occupies
   * table logic: does the layout_table_caption have to be inside the table block? can we pre-calculate the actual width for the caption? does the table offer a callback we can use to keep the caption on the same page as the table?
   * introduce object to store/organize running content data and specs
   * QUESTION: should theme font handle hierarchical keys (either explicitly or implicitly)
  
positive.code: == TODO
  
  * QUESTION should we show keys with hyphens instead of underscores in theming guide?
  
  * AsciiDoc table cell leaves padding below last block
  * go ahead and add separate padding control to label in admonition block; default to padding on content if not specified
  * M+ 1mn box drawings have width of 1000 instead of 500, so they don't draw box correctly (see https://github.com/prawnpdf/prawn/issues/1002)
    - looks like we're going to have to patch the font to draw the box lines correctly in a 500x860 space
    - might want to file this upstream
  
negative.code: * add a test suite
  * refactor as Prawn View
  * add support for footnotes (as article or chapter endnotes)
  * pass styles downwards to child elements in formatted text transform instead of decorating on way out of hierarchy
  * rework text handling in Prawn to support line height natively
  * margin collapsing (like CSS)
  * use proper model to handle the page number to current part/chapter/section mapping in running content
  * cleanup/reorganize imports in lib/asciidoctor/converter.rb
  
  == Documentation
  
  