fields: Default to cPickle unless we're debugging.
fields: Default to cPickle unless we're debugging.

cPickle is quite a few times faster than pickle but is difficult to debug.
Therefor when DEBUG is True we load pickle, otherwise we try to load cPickle
and only when that fails do we fall back to loading pickle.

bltravis/django-fields,svetlyak40wt/django-fields,bltravis/django-fields,nautilebleu/django-fields,svetlyak40wt/django-fields