Don't put payment specific settings in local_settings template.
Automated merge with ssh://bitbucket.org/stephenmcd/cartridge
Fix AttributeError with empty cart in Django 1.5

Django 1.5 looks for a pk in BaseInlineFormSet's __init__, which it couldn't find on EmptyCart. The fix adds the attribute with value None.
Merge
Only run stripe tests if its used, since it breaks Python 2.5 support (stripe package doesn't work in 2.5)
Fix class decorator for stripe tests for Python 2.5