Added simple dockerfile for the application.

[MrLokans]

Refers to issue #6

To test it locally:

# Build actual image
docker build .  -t needl
# Run it with no traces in system after completion
# Note that passing --daemon flag will make no sense with docker
docker run --rm $(docker images | grep needl | awk '{print $3}') --verbose

Here is an instruction how to actually tag and push the image built to the dockerhub: https://docs.docker.com/docker-cloud/builds/push-images/