plotting._stringify not unicode safe
/Users/germuska/.virtualenvs/data/lib/python2.6/site-packages/pandas/tools/plotting.pyc in _stringify(x)
   1073         return '|'.join(str(y) for y in x)
   1074     else:
-> 1075         return str(x)
   1076 
   1077 

UnicodeEncodeError: 'ascii' codec can't encode character u'\u2019' in position 1: ordinal not in range(128)

If labels can't be unicode, perhaps can a clearer error be thrown?
