Bump cryptography from 2.2.2 to 2.3

Bumps [cryptography](https://github.com/pyca/cryptography) from 2.2.2 to 2.3.
- [Release notes](https://github.com/pyca/cryptography/releases)
- [Changelog](https://github.com/pyca/cryptography/blob/master/CHANGELOG.rst)
- [Commits](pyca/cryptography@2.2.2...2.3)

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

Author: dependabot[bot]

requirements.txt

@@ -2,7 +2,7 @@ jinja2==2.10
 pgpubsub
 numpy==1.14.3
 PyYAML==3.12
-cryptography==2.2.2
+cryptography==2.3
 scikit-learn==0.19.1
 python-geoip==1.2
 python-geoip-geolite2==2015.303

requirements_unit_tests.txt

@@ -2,7 +2,7 @@ jinja2==2.10
 pgpubsub
 numpy==1.14.3
 PyYAML==3.12
-cryptography==2.2.2
+cryptography==2.3
 scikit-learn==0.19.1
 python-geoip==1.2
 python-geoip-geolite2==2015.303