Bump rsa version to latest version

Fixes the issue with new setuptools and python3.

For more info see: https://bitbucket.org/sybren/python-rsa/issue/17/pip-install-fails-on-python3-with-newer

Fixes #324.
Merge branch 'bump-rsa-package' into develop

* bump-rsa-package:
  Bump rsa version to latest version