Update utils.py

If the value contains special chars (like "Secondaire sup\xc3\xa9rieur"), rendering the widget fails...  It pass if we transform the value (v) to unicode before using zope.i18n.translate...

Please review and merge if everything seem ok...

Thank you,

Gauthier
Added test, turn str to unicode only if not already unicode...
Updated changelog
Merge remote-tracking branch 'plone/master'
Uncomment now that all tests pass...
Merge pull request #24 from gbastien/master

UnicodeDecodeError while translating the key of a vocabulary if it contains special chars