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Workaround environment variables for configuration, and bugfix.
- Feature 45 - ``DocuSignClient`` can be configured using environment
variables. Supported environment variables are: ``DOCUSIGN_ROOT_URL``,
``DOCUSIGN_USERNAME``, ``DOCUSIGN_PASSWORD``,
``DOCUSIGN_INTEGRATOR_KEY``, ``DOCUSIGN_ACCOUNT_ID``,
``DOCUSIGN_APP_TOKEN`` and ``DOCUSIGN_TIMEOUT``.
Obviously, arguments you explicitely pass to the constructor have priority
over environment variables.
Demo scripts were using environment variables with prefix
``PYDOCUSIGN_TEST_``. The environment variables have been renamed with
either ``DOCUSIGN_`` (the ones in the list above) or ``DOCUSIGN_TEST_``
prefix.
- Bug 44 - Using http://diecutter.io in
``pydocusign.test.generate_notification_callback_body()``. Secure URL was
broken because of SSL certificate.