Remove node restriction and allow $date objects

[bytesnz]

I have:

• removed the node version restriction as it works with the latest LTS version of node
• change the forIn function to allow for deep value substitution, for example for $date objects

db.events.aggregate([
    { "$match": { "event": "request", "time": { "$gte": { "$date": "$from" }, "$lt": { "$date": "$to" } }
])

• added a Dockerfile to generate a docker image that could be pushed to docker hub