message: docs: point our README the maintained Docker image
  Our README now points to a not-so-well-maintain, community-contributed
  Docker image. The docker image we link to here is managed and
  supported by actual committers under the Preset org.
diff: @@ -103,7 +103,7 @@ Installation & Configuration
  Resources
  -------------
  * [Mailing list](https://lists.apache.org/list.html?dev@superset.apache.org)
  -* [Docker image](https://hub.docker.com/r/amancevice/superset/) (community contributed)
  +* [Docker image](https://hub.docker.com/r/preset/superset/)
  * [Slides from Strata (March 2016)](https://drive.google.com/open?id=0B5PVE0gzO81oOVJkdF9aNkJMSmM)
  * [Stackoverflow tag](https://stackoverflow.com/questions/tagged/apache-superset)
  * [Join our Slack](https://join.slack.com/t/apache-superset/shared_invite/enQtNDMxMDY5NjM4MDU0LWJmOTcxYjlhZTRhYmEyYTMzOWYxOWEwMjcwZDZiNWRiNDY2NDUwNzcwMDFhNzE1ZmMxZTZlZWY0ZTQ2MzMyNTU)
  