Proper labeling for figures nested in Parts.
Merge pull request #135 from oreillymedia/gh-pages

Updated spec document formatting
Regression tests to ensure url.in.parens handling works as expected for callout markers.
Merge pull request #136 from oreillymedia/labels

Proper labeling for formal elements nested in parts
Fixing bug where NCX dtb:uid identifier did not sync up with OPF unique-identifier when default identifier values were generated.
Merge pull request #137 from oreillymedia/labels

Improved default handling of NCX/OPF identifiers
Fixed bugs in handling of formal object labeling (figure/table/example) in use cases with Parts.
Handling to exclude "informal" figures and tables from count when labeling fig/table captions.
No label generated for empty figure caption or table caption.
Merge pull request #139 from oreillymedia/labels

Improvements/fixes in formal object labeling
Renaming variables and updating comments in get-param-value-from-key template to reflect generalized usage.
Adding parameterized handling via xref.elements.pagenum.in.class to add "pagenum" class values to XREFs to facilitate use of CSS Paged Media to add page numbers for paged outputs.
Merge pull request #141 from oreillymedia/pagenums

Parameterized handling for "pagenum" classes for print outputs
Adding numeration localizations for English.
Merge pull request #142 from oreillymedia/localizations

Adding numeration localizations for English.
Handling for audio/video assets in EPUB OPF manifest.
Merge pull request #143 from oreillymedia/audio-video

Handling for audio/video assets in EPUB OPF manifest.
Adding toc.section.depth parameter to all "tocgen" templates and passing it via all invocations of these templates; will allow for more control over toc depth in books that have multiple TOCs (e.g., mini toc and full toc).
Merge pull request #145 from oreillymedia/toc-refactor

Tocgen template refactor
Fixed bug in start-of-text guide element generation when book does not have titlepage or cover.