django 1.9 incompatible

[François GUÉRIN]

django-bleach is not compatible with django 1.9, due to:

https://docs.djangoproject.com/en/1.9/internals/deprecation/

django_bleach/forms.py has an import like:

from django.utils.importlib import import_module

which should be replaced by:

try:
    # Django versions >= 1.9
    from django.utils.module_loading import import_module
except ImportError:
    # Django versions < 1.9
    from django.utils.importlib import import_module