anchor.diff:  * Document theme-related AsciiDoc attributes in theming guide (#428)
   * Section title alignment should be customizable via theme (#343)
   * Collapse all whitespace when normalizing (#355)
  -* Require space on either side of math operator to avoid interpretting dates as math equations (#429)
  +* Require space on either side of math operator to avoid interpreting dates as math equations (#429)
   * Allow specifying a font style for a title on the title page (#423)
   * Fix Prawn SVG to support arrow heads on lines (#75)
   * Upgrade prawn-svg to 0.25.1
  
positive.code: 
  == 1.5.0.alpha.13 (2016-09-19) - @mojavelinux
  
  * Add support for mirror (recto/verso) margins and facing pages when media=prepress
  * Add non-breaking hyphen glyph to built-in fonts so its intended behavior is honored (#462)
  * Add page break before a book part (#329)
  * Allow running (header/footer) content to be arranged in columns (#449)
  
negative.code: * Resolve bare image-related attribute values relative to base_dir
  * Only allow Prawn SVG to fetch remote images if the allow-uri-read attribute is set (#548)
  * Introduce page_margin_inner and page_margin_outer keys to theme
  * Start title page, toc, main content, parts, and chapters on recto page when `media=prepress` and `doctype=book`
  * Allow default font style for table to be set via theme (`table_font_style`)
  * Use correct default bullet per nested unordered list level (#529)
  * Call `start_new_part` at start of each book part
  * Delegate to `layout_part_title` method to layout part title
  * Don't match a special section as a chapter unless the doctype is book
  * Fix list marker placement when list item touches bottom of page
  * Eliminate excessive spacing between list items that contain nested lists
  * Drop lines in running (header/footer) content with unresolved attributes (#522)
  * Ensure `start_new_chapter` is always executed at a chapter transition (#524)
  * Add support for root xref (e.g., &lt;&lt;included-doc#&gt;&gt;) (#521)
  * Prevent block from spilling to next page if there's no more content (#361)
  * Add support for px units to pdf-page-size attribute
  