Update minimum Docker version

According to the official docs at:
https://docs.openshift.org/latest/install_config/install/prerequisites.html

CONTRIBUTING.adoc

@@ -45,7 +45,11 @@ Here's how to get set up:
 1. For Go, Git and optionally also Docker, follow the links below to get to installation information for these tools: +
 ** http://golang.org/doc/install[Installing Go]. You must install Go 1.4 and NOT use $HOME/go directory for Go installation.
 ** http://git-scm.com/book/en/v2/Getting-Started-Installing-Git[Installing Git]
-** https://docs.docker.com/installation/[Installing Docker]. NOTE: OpenShift requires Docker 1.7.1 or higher.
+** https://docs.docker.com/installation/[Installing Docker].
+
+NOTE: As of now, OpenShift requires Docker 1.8.2 or higher.
+The exact version requirement is documented https://docs.openshift.org/latest/install_config/install/prerequisites.html#installing-docker[here].
+
 2. Next, create a Go workspace directory: +
 +
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