anchor.diff:  
   * conversion of single file (no master document)
   * package images referenced by content
  -* do we need the SVG property if the HTML links to an SVG document?
   * how custom CSS is specified
   
   == NOTES
  
positive.code: * allow role to be applied to chapter (which means the role must be on the document)
  * make sure every doc is assigned an ID (perhaps it already is) so we don't need to rely on the docname attr as a fallback
   ** I believe this is already true; just remove hack
  * only add svg property to spine item for front matter file if SVG is detected
  * should we enable hyphens in non-Kindle?
   ** we can reenable once we confirm it doesn't crash Kindle for Mac
  * switch to epubcheck-ruby
  
negative.code: 
  == TODO
  
  * remove text justification hack (#92) (PR sent)
  * warn in case when target of inter-document xref can't be resolved, but xref has explicit text
  * don't add image from front matter if already referenced by chapter
  * add document filename to warn messages
  * look for front-matter.html relative to docdir (or base_dir?); also allow front-matter.xhtml
  * cleanup stashes
  * change references[:spine] to spine_document property
  * add helper to resolve imagesdir
  * support inline SVG
  * describe the leveloffset setting in more detail
  * link to https://medium.com/@sandersk/responsive-ebook-design-a-primer-8bba01328219 in style section in README
  * why don't we just use the chapter filename as the id?
  * only uppercase document title if detected in CSS
  * add empty front matter page in kf8 version if one is specified to allow navigation to first entry from TOC
  