fix: extra_attributes as a set
Merge pull request #22 from satra/fix/extra_attrib

fix: extra_attributes as a set
Minor code improvements
fix persistence unit test : UnicodeEncodeError: 'ascii' codec can't encode character u'\u1ef3'
Merge pull request #23 from jdcourcol/master

fix persistence unit test : UnicodeEncodeError: 'ascii' codec can't enco...

Many thanks, @jdcourcol!
Added: Support initialising namespaces when creating a ProvBundle
Fixed: Triple quoted multi-line string literals in PROV-N
Fixed: Parsing XSD dateTime
Fixed: Refactor the flattening code
Improved the management of QName
fix: resolve conflicts