Add RDFConverter#bdsk_url
Add RDFConverter#date_modified
Add institution as fallback to #publisher
Add one more bdsk-file field to RDFConverter::DEFAULT_REMOVE_FROM_FALLBACK
Fix #type
Fix #year

Could return "2014-" instead of "2014"
Add "Dissertation" to #thesis_degree
Remove :type from fallback when it has a thesis degree
Add #annote
Fix test
Fix #title
Also allow semicon as separator in #keywords
Merge pull request #84 from tmaier/master

Follow-up to #83 - RDFConverter