Added dockerfile

Seems so obvious, so why is there none? Useful for deployment (perhaps outside of CoreOS) or development.

This docker file builds an image, which launches the binary automatically. To build:

    docker build -t coreos/etcd .

To run:

    docker run -d coreos/etcd

any arguments you pass, will be passed to the etcd binary (in addition to the flags to bind to 0.0.0.0, otherwise it won't work):

    docker run -t -i coreos/etcd --help