update readme

README.md

@@ -17,42 +17,9 @@ Default values: (set them in your `docker_config` to overwrite)
 
 ### `docker_version`
 
-Specify the version of Docker to install, e.g. `1.12.6`, `17.05`.
+Specify the version of Docker to install, e.g. `1.12.6`, `17.05`. It allows to upgrade to latest version by specifying `latest`.
 
-Default value: `17.03`
-
-### `docker_setup_script_md5_sum`
-
-Default value: md5 checksum of default `docker_version` setup script (see `defaults/main.yml` for exact default value)
-
-**If you intend to install a version of Docker other than the default, you must provide an appropriate override value for this variable.**
-
-Either:
-
-1. Generate an md5 checksum for the desired version's install script
-1. If you know what you are doing and are not worried about security, set this variable to "no" or "false" to disable checksum verification of the setup script.
-
-### `docker_setup_script_url`
-
-URL pointing to a Docker setup script that will install the specified `docker_version`.
-
-Default value: `https://releases.rancher.com/install-docker/{{ docker_version }}.sh`
-
-The default URL utilizes [Rancher Labs' version-specific, OS-agnostic setup scripts](https://github.com/rancher/install-docker), which in turn just install the appropriate version of `docker-ce` or `docker-engine` from the official Docker `apt` and `yum` repositories.
-
-### `docker_upgrade`
-
-Per default, this role will only download and run the installation script when
-Docker is not installed (or more precise: when `dockerd` is not in `$PATH`). Set
-`docker_upgrade` to `True` to override this behavior and force the install
-script to be run.
-
-So in order to upgrade Docker on managed systems, take the following steps:
-
-0. Either download a newer version of this role (with a more recent default
-   version) or update `docker_version` and `docker_setup_script_md5_sum` in your
-   host/group vars.
-1. Run your playbook with `-e docker_upgrade=True`
+Default value: `17.06`
 
 ### `docker_proxy`, `docker_http_proxy`, `docker_https_proxy`, `docker_no_proxy`