Added a Dockerfile

Please find in this PR a Dockerfile suitable to build a running BabitchClient container.

# How to use

At the root of the project:

    docker build -t m6web/babitch-client .

Then run the container:

    docker run -p 8000:80 m6web/babitch-client

You now have a BabitchClient listening on port `8000`!

# Why do we want this?

Because Stage1. I think I already told most of you about Stage1, but I'll sum up the service quickly for the others. Stage1 is an automated staging platform. It hooks up with your GitHub repositories, and builds running instances of your projects everytime you push, for every branch.

Now that (experimental) support for Dockerfiles has landed in Stage1, it's trivial to support any kind of project. For example, each time I push on the `docker` branch of `ubermuda/BabitchClient`, Stage1 builds a new container with my new code and I can then access a staging instance at http://docker.ubermuda.babitchclient.stage1.io/?nobackend. It also integrates with GitHub's status API so you get the staging instance URL automatically in every PR on your repo.

This way, each time you push, it becomes trivial to show users a working version your PR.

For example, I build an instance of BabitchClient that you can see there : http://docker.ubermuda.babitchclient.stage1.io/?nobackend#/

And if you don't want to use Stage1, well, it's still a working Dockerfile for BabitchClient, meaning you can easily fire up a working BabitchClient instance for your demos :)