Merge pull request #2729 from shin-/bump_docker_py

Use latest docker-py rc

requirements.txt

@@ -1,9 +1,9 @@
 PyYAML==3.11
 cached-property==1.2.0
+docker-py==1.7.0rc2
 docopt==0.6.1
 enum34==1.0.4
 git+https://github.com/d11wtq/dockerpty.git@29b1394108b017ef3e3deaf00604a9eb99880d5e#egg=dockerpty
-git+https://github.com/docker/docker-py.git@master#egg=docker-py
 jsonschema==2.5.1
 requests==2.7.0
 six==1.7.3