Fixed #22218 -- Deprecated django.conf.urls.patterns.

Thanks Carl Meyer for the suggestion and Alex Gaynor and Carl for reviews.
Fixed #22372 -- Improved description of WizardView.get_context_data().

Thanks simon29 for the report.
Fixed typo in 1.8 release notes.
Cleaned up string detection for a deprecation warning by using six.string_types.
Fixed #22363 -- Correctly serialize `django.utils.datetime_safe` objects.

Thanks to linovia for the report.
Refactored and commented strip_tags utility