Test lazy translation objects and Unicode labels
`force_text()` on labels.

`__str__` must return `str` objects, not proxies, so in case Django's lazy
translations are used as labels, force them into text when required.
Merge branch 'lazy-translations'

* lazy-translations:
  `force_text()` on labels.
  Test lazy translation objects and Unicode labels
Bump to 0.6.2