Use RFC5051 if 'unicode_collation' isn't specified.

This is a much nicer default than just using `compare`.
Version bump to 0.1.1.
Fixed stringify so it handles spaces, code, etc.
Version bump to 0.1.1.1.
Improvements to bibtex2pandoc.hs.

* Added isBibtex parameter so pure bibtex can be treated differently.
* Added --bibtex flag on command line.
* Added toLiteralList.
Drop leading spaces in abbrevs file (otherwise json parse fails).
bibtex2pandoc: start on BibM monad.
More improvements to bibtex2pandoc.
Completed monadic dsl for bibtex2pandoc.
bibtex2pandoc: Start on crossref resolution.
More bibtex2pandoc improvements.
bibtex2pandoc: Started implementing biblatex crossrefs.
bibtex2pandoc:  Finished biblatex crossref handling.
bibtex2pandoc:  Added isPresent, cleaned up.
Nick Bart's changes to bibtex2pandoc.hs.
Typo in biblatex crossref field conversion.
Fixed biblatex crossrefs.
Use standard monadic/applicative interface.  Remove ==>.
Use opt instead of optional.
bibtex2pandoc: Apply unTitlecase transformation.

This requires the latest pandoc from github.