Automate New version

[F-Eckhard]

Hi Wernight,

First, thanks for this dockerfile, helps a lot ;)

One suggestion for this would be to automaticaly get the newest version:

RUN apk add --update curl &&
rm -rf /var/cache/apk/*

RUN VERSION=$(curl -s https://storage.googleapis.com/kubernetes-release/release/stable.txt) && curl https://storage.googleapis.com/kubernetes-release/release/$VERSION/bin/linux/amd64/kubectl >> /usr/local/bin/kubectl

[veeramarni]

@wernight do you need a pull request based on the above suggestion?

[wernight]

Sounds good to me.