Adding a file to build a docker container and simple makefile

I got this working so I can test out how nodejs will work in
side of docker, and maybe start to use docker for deploying
nodejs apps internally. This should work and I had pullreq
running 100% locally.

Once you have docker working you should be able to just do
a `make build` to kick off the docker build.  And then you can
run the container by doing something like:

docker run -it \
    -p 9095:9095 \
    -e PORT=9095 \
    -e MONGOLAB_URI="mongodb://xxxx/pullreq" \
    -e SESSION_SECRET="xyz" \
    -e GITHUB_CLIENT_ID="your_client" \
    -e GITHUB_CLIENT_SECRET="your_secret" \
    charliek/pullreq