replace django.utils.hashcompat with hashlib

The compatibility modules django.utils.copycompat and django.utils.hashcompat as well as the functions django.utils.itercompat.all and django.utils.itercompat.any will be removed. The Python builtin versions should be used instead.

https://docs.djangoproject.com/en/1.4/internals/deprecation/#id3
Totally agree. I replaced it with hashlib.sha1 because I found this as a recommendation on django page, but we can replace it with default_token_generator.