code: def bib_path(self):
          
          bib_name = self.bib_name
          # FIXME need to bake in search paths for tex documents in all platforms
          osx_path = os.path.expanduser(
              "~/Library/texmf/bibtex/bib/{0}".format(bib_name))
          if self._file_exists(bib_name):
              return bib_name  # bib is in project directory
          elif os.path.exists(osx_path):
              return osx_path
          else:
              return None
docs: Absolute file path to the .bib bibliography document.