Bump cryptography from 2.3.1 to 2.6.1

Bumps [cryptography](https://github.com/pyca/cryptography) from 2.3.1 to 2.6.1.
- [Release notes](https://github.com/pyca/cryptography/releases)
- [Changelog](https://github.com/pyca/cryptography/blob/master/CHANGELOG.rst)
- [Commits](pyca/cryptography@2.3.1...2.6.1)

Signed-off-by: dependabot[bot] <support@dependabot.com>

homeassistant_cli/package_constraints.txt

@@ -6,7 +6,7 @@ bcrypt==3.1.4
 certifi>=2018.04.16
 jinja2>=2.10
 PyJWT==1.6.4
-cryptography==2.3.1
+cryptography==2.6.1
 pip>=8.0.3
 pytz>=2018.07
 pyyaml>=4.2b1