feat(docker): add basic Dockerfile

We start to support Docker(basic)

• https://hub.docker.com/r/honkit/honkit

Installation

docker pull honkit/honkit

Usage

Show help

$ docker run -v `pwd`:`pwd` -w `pwd` --rm -it honkit/honkit honkit  --help

Build

$ docker run -v `pwd`:`pwd` -w `pwd` --rm -it honkit/honkit honkit build

We need to improve docker support.
For example, we want to get ebook-convert integration for honkit pdf or honkit epub

refs #32