Upgrade cryptography to version 3 (#620)

Author: antusus

.gitignore

@@ -80,3 +80,6 @@ target/
 
 # Misc
 tokens.pk
+
+#pyenv
+.python-version

setup.py

@@ -63,7 +63,7 @@ def main():
         'wrapt>=1.10.1',
     ]
     redis_requires = ['redis>=2.10.3']
-    jwt_requires = ['pyjwt>=1.3.0', 'cryptography>=0.9.2']
+    jwt_requires = ['pyjwt>=1.3.0', 'cryptography>=3']
     extra_requires = defaultdict(list)
     extra_requires.update({'jwt': jwt_requires, 'redis': redis_requires, 'all': jwt_requires + redis_requires})
     conditional_dependencies = {