anchor.diff:  * fix labels in issue tracker to match other projects; in particular, enhancement should be green.
   * start the README with a proper introduction to Asciidoctor PDF (and not so focused on Prawn)
   * setup asciidoctor-mathoid project, then mention it in the STEM support section
  -
   * QUESTION should we show keys with hyphens instead of underscores in theming guide?
   
  -* prawn-svg upgrade broke sizing of title logo image; perhaps others
  +.1.5.0.alpha.16
  +* support unnumbered and no-bullet style on ordered list
  + ** see https://github.com/asciidoctor/asciidoctor/pull/2286
  +* fix warnings in Ruby 1.9.3
  +* remove hack to add trailing endline to source for rouge (now fixed in rouge)
  + ** set minimum rouge version
   * document how to install Asciidoctor PDF for Ruby 2.0.0 (since Prawn now requires 2.1.0)
  +
  +//-
  +* should we reroute String#downcase if unicode gem is loaded? this is required for natural cross references; or should we just document workaround?
  +* if sourcemap is enabled, error messages should include whatever line information is available
  +* CRITICAL: prawn-svg upgrade broke sizing of title logo image; blocking release
  + ** see https://github.com/mogest/prawn-svg/issues/96
  +* Prawn reports unknown blank font if family is valid but style is invalid (see https://github.com/prawnpdf/prawn/issues/1022)
  +* catch UnsupportedImageType and issue warning that suggests using prawn-gmagick; see sandbox/interlaced.png
  +* something like prawn-gmagick in Java env
  +* look for image in imagesoutdir if set and the image cannot otherwise be resolved
  +* in follow-up to #271, mention that images are resolved at the time of conversion; thus, they need to be located where the converter can find them; that often means setting imagesdir to an absolute path
   * split out the background fill from PR 664 into a separate PR to merge sooner
   * apply logic for convert_sidebar to convert_example
   * implement SVG fit for background image (#765)
  -* vertical centering in table cell w/ Noto Serif is off
  +* vertical centering in table cell w/ Noto Serif is off (set align to vertical center for a single-line cell)
   * import generate-font-subsets.pe script from Asciidoctor EPUB3; rename to generate-bundled-fonts.pe
   * if we assume that any block except a paragraph will "unfloat", we might be able to implement floating images; just mark the "jump to point" for any block that isn't a paragraph, restrict the width and write
  +* update the theme-schema.json (or remove it)
   * have some sort of threshold for how close we get to bottom of page before advancing when starting new block
   * look where else we should be using advance_page instead of start_new_page
    ** do we really need advance_page when drawing background? isn't that always forging a new page?
  
positive.code: * define sum on core_ext/array to optimize for Ruby 2.4
  * allow border bottom of table header row to be set by theme
  * vertically center background image by default (yes?)
  * stroke and fill multi-page sidebar block (#259) and example block (#362)
   ** see PR
  * 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
  * line height in TOC is too small if heading only contains monospaced text
  * UPSTREAM: highlighting of CSS w/ rouge seems messed up; don't recognize keywords
   ** compare with pygments
   ** rouge also incorrectly identifies an endline in a schemaLocation attribute as an error
  * FIXME: stop using fallback fonts in default theme (instead, bundle a fuller font)
   ** using fallback fonts significantly slows down Prawn because it checks every letter every time (see https://github.com/prawnpdf/prawn/blob/master/lib/prawn/text/formatted/box.rb#L427-L434)
   ** add broader character range to monospace font so we can drop fallback font by default (#282)
  
negative.code: * should we drop "<font>" handler in formatted text transform?
  * ttfunk 1.5.0 chokes on narrow no-break space char \u202f (patch applied; https://github.com/prawnpdf/ttfunk/issues/39)
  * implement text transform for running content (#702)
  * implement line highlighting in rouge (#681)
  * should we allow the template/format of the line number in the source listing to be controlled using a sprintf template?
  * only nest outline inside of root if doctype=article (still valid?)
  * warn if image in running content can't be found (#731)
  