Parts with content are now included in back/forward navigation in webbooks.
Don't show invisible parts in back/forward navigation in webbooks.
Extraneous parenthesis.
NCX generation now supports invisible parts.
Maybe fix EPUB NCX validation error?
Revert "SVG files are now enabled."

This reverts commit 213c8a269db0a3c566baed35772813945ca53cf3.
replacing deprecated wp calls
Merge branch 'dev' of https://github.com/pressbooks/pressbooks into dev
Merge pull request #49 from bdolor/dev

replacing deprecated wp calls
Merge branch 'dev' of https://github.com/pressbooks/pressbooks into dev
Merge branch 'dev' into epub3