Upgrade requirements.txt

requirements.txt

@@ -5,12 +5,12 @@ certifi==2018.4.16
 cffi==1.11.5
 chardet==3.0.4
 cryptography==2.3
-docker==3.3.0
-docker-pycreds==0.2.2
+docker==3.5.1
+docker-pycreds==0.3.0
 idna==2.6
 pycparser==2.18
-pyOpenSSL==17.5.0
-PyYAML==3.12
+pyOpenSSL==18.0.0
+PyYAML==3.13
 requests==2.18.4
 six==1.11.0
 urllib3==1.22