Push to auto-deploy

I'm gonna be adding this in two parts, this is the first one.

This service takes a personal access token and and automatically creates a deployment in the API when the default branch is pushed to.

I've started on a [hubot script](https://github.com/atmos/hubot-auto-deploy) that will hook into the API and allow you to enable/disable from chat. The eventual goal of all of this being that auto-deployment is a consolidated feature and not something that each deployment system has to implement itself.

The next wave of this will be responding to commit status events and requiring certain contexts to be present and auto-deploying more complicated workflows.
The payloads are different in status events so I figured we should get push to deploy going before we start differentiating between payloads.