Fallback for UUID generation
Merge pull request #473 from dginev/uuid_fallback

Fallback for UUID generation
refactored the MakeBibliography to not modify the postprocessor and more consistently convert various forms that the bibliographies might take; no longer looks for bib.xml, however; also clarified comments
the format option to CrossRef is changed to extension because that's really how it's used
renamed the 'html' stylesheet to 'html4' to be clear
renamed the 'html' stylesheet to 'html4' to be clear
Changed the --format option to make html mean html5, to make html4 explicit; to pass the desired file extension to CrossRef instead of the format