Update Docker config and doc

docs/docker.markdown

@@ -1,13 +1,24 @@
-How to test Kanboard with Docker?
-=================================
+How to run Kanboard with Docker?
+================================
 
-Kanboard can run with [Docker](https://www.docker.com).
+Kanboard can run easily with [Docker](https://www.docker.com).
 There is a `Dockerfile` in the repository to build your own container.
 
+Use the automated build
+-----------------------
+
+Every new commit on the repository trigger a new build on [Docker Hub](https://registry.hub.docker.com/u/kanboard/kanboard/).
+
+```bash
+docker run -d --name kanboard -p 80:80 -t kanboard/kanboard:latest
+```
+
+The tag **latest** is the **development version** of Kanboard, use at your own risk.
+
 Build your own Docker image
 ---------------------------
 
-From your kanboard directory run the following command:
+Clone the Kanboard repository and run the following command:
 
 ```bash
 docker build -t youruser/kanboard:master .
@@ -22,8 +33,14 @@ docker run -d --name kanboard -p 80:80 -t youruser/kanboard:master
 Store your data on a volume
 ---------------------------
 
-You can also save your data outside of the container, on the local machine:
+By default Kanboard will store attachments and the Sqlite database in the directory data. Run this command to use a custom volume path:
 
 ```bash
 docker run -d --name kanboard -v /your/local/data/folder:/var/www/html/data -p 80:80 -t kanboard/kanboard:master
 ```
+
+References
+----------
+
+- [Official Kanboard images](https://registry.hub.docker.com/u/kanboard/kanboard/)
+- [Docker documentation](https://docs.docker.com/)