[WIP] Add Dockerfile

[recrsn]

Closes #84

• Based on node:6 standard docker image

[jacogreyling]

Thanks Amitosh! I see you're using both forms of ENV in your Dockerfile. Please pick one and stick with it for consistency. As you know with the latter form (with the = sign) you can have multiple env's in one definition and it's actually preferred, as per this statement, "...the first form [ref to = annotation] is preferred because it produces a single cache layer.". Then I also suggest you add the LABEL instruction with a 'description' which you can take from the package.json. Then probably the biggest one, we need Node 8 not 6 :) I take it you're going to create containers for mongodb and redis as well? Thanks again for your contribution! It's much appreciated.