add a test for unicode tags and TaggedItems
remove @python_2_unicode_compatible from models without __str__
fix unicode error in TaggedItem.__str__ on py2

this was caused by trying to format unicode data into
a byte string
Merge branch 'release/v0.3.3' into develop
Merge branch 'master' of https://github.com/starshipfactory/django-tagging into feature/fix-unicode-issues
One import per lines
Merge branch 'feature/fix-unicode-issues' into develop
Updating CHANGELOG
Bumping to version 0.3.4
Merge branch 'release/v0.3.4'