Merge pull request #36 from OwnCA/setup_cryptography_>=3.2

Update setup.py cryptography to >=3.2

setup.py

@@ -9,7 +9,7 @@
 here = os.path.abspath(os.path.dirname(__file__))
 
 packages = ["ownca", "ownca/crypto"]
-requires = ["cryptography>=2.8", "voluptuous>=0.11.7"]
+requires = ["cryptography>=3.2", "voluptuous>=0.11.7"]
 test_requirements = ["pytest>=3"]
 about = {}