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. Dropped support for old Django versions. Only the upstream supported
versions are now supported, currently 1.8, 1.9, and 1.10.
. Made recaptcha checking use SSL by default. This can be disabled by setting
``RECAPTCHA_USE_SSL = False`` in your Django settings or passing
``use_ssl=False`` to the constructor of ``ReCaptchaField``.
. Made ReCaptchaField respect required=False