AWS Elastic Beanstalk support

Creating a deployable hubot (via `hubot -c`) doesn't Just Work™ when deploying to AWS Elastic Beanstalk out of the box - it was unable to find a start script to get it running.

I copied the same command used by foreman in `Procfile` (primarily for Heroku) and placed it in package.json as a start script. EB is now able to successfully start hubot (`npm start` will now work as well).

* Notes
  * AWS Container Type: 64bit Amazon Linux running Node.js
  * This change does create some minor duplication between `Procfile` and `package.json`