add fig.yml and Dockerfile to ease testing and development

I would like to contribute a [fig.yml](http://www.fig.sh) and Dockerfile
It allows to spin up multiple docker containers with the wiki app.
Also allows to add redis and couchdb [...] containers to the mix and run these with wiki(0-conf)
It provides a reproducible development and even some day production ready environment.

I would also be possible to test farming/federation among several app containers.
interested? PR on the way