Avoid crash when there is nothing to affix.
Merge pull request #19 from davidlesieur/affixed-wrap-none

Avoid crash when there is nothing to affix.
Testcase for handling non-ascii character
Allow specifying the encoding of the BibTeX DB

- raise BibTeXDecodeError when decoding fails, passing the line number
  the decode error occurred on
- update the test case

Closes #20
Fix BibTeX month to CSL month mapping (fixes #24)
Merge branch 'master' of github.com:brechtm/citeproc-py