text: Title: Processbar issues
  Body: Looks like this needs to be converted to support python 3:
  ```
  File "/Users/rich/.pyenv/versions/3.5.2/lib/python3.5/site-packages/shop/cascade/processbar.py", line 85, in get_identifier
      content = unicode(Truncator(content).words(3, truncate=' ...'))
  NameError: name 'unicode' is not defined
  ```
  Option examples:
  ```
  # Python 2 and 3: alternative 1
  from builtins import str
  templates = [u"blog/blog_post_detail_%s.html" % str(slug)]
  # Python 2 and 3: alternative 2
  from builtins import str as text
  templates = [u"blog/blog_post_detail_%s.html" % text(slug)]
  ```