Update requirements to include docker[tls] packages

requirements.txt

+asn1crypto==0.24.0
 backports.ssl-match-hostname==3.5.0.1
 backports.weakref==1.0.post1
-certifi==2018.1.18
+certifi==2018.4.16
+cffi==1.11.5
 chardet==3.0.4
+cryptography==2.2.2
 docker==3.2.1
 docker-pycreds==0.2.2
 idna==2.6
-pkg-resources==0.0.0
+pycparser==2.18
+pyOpenSSL==17.5.0
 PyYAML==3.12
 requests==2.18.4
 six==1.11.0