anchor.diff:  * look for correct file to require in bin script
   * upgrade prawn-icon from 1.3.0 to 1.4.0
   * upgrade rouge to 2.2.1 
  -* add concurrent-ruby to runtime dependencies for compatiblity w/ Asciidoctor 1.5.8
  +* add concurrent-ruby to runtime dependencies for compatibility w/ Asciidoctor 1.5.8
   
   == 1.5.0.alpha.16 (2017-07-30) - @mojavelinux
   
  
positive.code: * normalize space characters in authors content and drop lines with unresolved attribute references (#1642)
  * skip image block with missing image if computed alt text resolves to empty string (#1645)
  * custom theme does not inherit from base theme by default; must be specified explicitly using `extends: base` (#1640)
  * allow theme to confiure number of index columns using `index_columns` key (#1663)
  * configure AsciiDoc table cell to inherit font properties from table and scale font size of nested blocks (#926)
  * scale font size of literal table cell (#1696)
  * add support for id attribute on link macro
  
negative.code: 
  == 1.5.0.rc.2 (2020-01-09) - @mojavelinux
  
  * patch Prawn to fix incompatibility with Ruby 2.7 (to fix text wrapping)
  * fix crash when assigning font style to header cell in table body (#1468)
  * fix parsing of array value of pdf-page-margin attribute (#1475)
  * fix warning when reading data from a remote URL when running with Ruby 2.7 (#1477)
  