Stop using dockerfile/* images

[thockin]

As per
http://blog.docker.com/2015/03/updates-available-to-popular-repos-update-your-images/
docker has stopped answering dockerfile/redis and dockerfile/nginx. Fix all
users in our tree. Sadly this means a lot of published examples are now broken.

I don't know why they didn't just make these aliases to their replacements. Sigh.

Fixes #6914

[thockin]

Please review carefully - this was done mostly mechanically.

[thockin]

Running e2e now

[a-robinson]

It looks like this breaks the unit tests

--- FAIL: TestReadme (0.10s)
    examples_test.go:262: ../examples/walkthrough/README.md did not validate correctly: [spec.containers[0].image: required value]
    examples_test.go:247: skipping (yaml): 
        ...
            volumes:
              - name: redis-persistent-storage
                source:
                  emptyDir: {}
        ...
    examples_test.go:247: skipping (yaml): 
        ...
                volumeMounts:
                    # name must match the volume name below
                  - name: redis-persistent-storage
                    # mount path within the container
                    mountPath: /data/redis
        ...
FAIL
coverage: 0.0% of statements
FAIL    github.com/GoogleCloudPlatform/kubernetes/examples  0.587s

[thockin]

The regex for extracting sample code was broken. Fixed in newest push, starting e2e now

[thockin]

@smarterclayton for regex and related comment

[a-robinson]

The spacing got put in the wrong spot :)

[a-robinson]

LGTM other than the one messed up line. Thanks for adding comments to the regex!

[thockin]

fixed the messed up line, e2e is still running

[smarterclayton]

Looks fine to me.

[thockin]

e2e SUCCESS!