Added Dockerfile for rapid deployment

By building an image from this Dockerfile, users can quickly setup a container running openbay without any additional setup:

```sh
$ docker build -t openbay .
$ docker run -d -p 80:80 openbay
``` 

Additionally, an automated build[1] can be created on Docker Hub to automatically build images of this Dockerfile, so all a user needs to do is pull the image.

See:

- #31 for more info.
- [1] [http://docs.docker.com/docker-hub/builds/](http://docs.docker.com/docker-hub/builds/)