Create Dockerfile

This will be useful for docker-only systems (like CoreOS). Using `ENTRYPOINT` will allow to use it like command:

```sh
$ docker run -d --name dockstash wayfin/dockstash --hosts <docker-hosts> --logstash <logstash-host:port>
```
Add every directory so .git is not there, and use another node base.
Merge pull request #5 from wayfin/imanel-patch-1

Imanel patch 1