Bump cryptography from 2.3.1 to 3.2

Bumps [cryptography](https://github.com/pyca/cryptography) from 2.3.1 to 3.2.
- [Release notes](https://github.com/pyca/cryptography/releases)
- [Changelog](https://github.com/pyca/cryptography/blob/master/CHANGELOG.rst)
- [Commits](pyca/cryptography@2.3.1...3.2)

Signed-off-by: dependabot[bot] <[email protected]>

Author: dependabot[bot]

requirements.txt

@@ -3,7 +3,7 @@ PyJWT==1.7.0
 #need 2.x for Python3 support
 python-dateutil==2.1.0
 #1.1.0 is the first that can be installed on windows
-cryptography==2.3.1
+cryptography==3.2
 #for testing
 httpretty==0.8.14
 pylint==1.5.4