Remove intro and link to Dockerhub

docker/README.md

 # GitLab Docker images
-## What is GitLab?
-
-GitLab offers git repository management, code reviews, issue tracking, activity feeds, wikis. It has LDAP/AD integration, handles 25,000 users on a single server but can also run on a highly available active/active cluster.
-Learn more on [https://about.gitlab.com](https://about.gitlab.com)
+The GitLab docker image is [available on Docker Hub](https://registry.hub.docker.com/u/gitlab/gitlab-ce/).
 ## After starting a container
@@ -165,4 +162,4 @@ sudo docker push gitlab/gitlab-ce:latest
 ## Troubleshooting
-Please see the [troubleshooting](troubleshooting.md) file in this directory.
+Please see the [troubleshooting](troubleshooting.md) file in this directory.
\ No newline at end of file

[Sid Sijbrandij]

/cc @ayufan

[Kamil Trzcińśki]