DOCKER_VERSION and docker-version havn't been implemented.

So far, it looks like the declarations are not used, and so its safer not to
confuse people into thinking they do something.

Docker-DCO-1.1-Signed-off-by: Sven Dowideit <SvenDowideit@docker.com> (github: SvenDowideit)
Upstream-commit: 6ed610fb8014d500e001bb0677f0e1af0dc9312d
Component: engine

components/engine/docs/sources/examples/nodejs_web_app.md

@@ -59,12 +59,8 @@ Create an empty file called `Dockerfile`:
     touch Dockerfile
 
 Open the `Dockerfile` in your favorite text editor
-and add the following line that defines the version of Docker the image
-requires to build (this example uses Docker 0.3.4):
 
-    # DOCKER-VERSION 0.3.4
-
-Next, define the parent image you want to use to build your own image on
+Define the parent image you want to use to build your own image on
 top of. Here, we'll use
 [CentOS](https://registry.hub.docker.com/_/centos/) (tag: `centos6`)
 available on the [Docker Hub](https://hub.docker.com/):
@@ -108,7 +104,6 @@ defines your runtime, i.e. `node`, and the path to our app, i.e. `src/index.js`
 
 Your `Dockerfile` should now look like this:
 
-    # DOCKER-VERSION 0.3.4
     FROM    centos:centos6
 
     # Enable EPEL for Node.js