Make dev setup and startup easier

On my first-time install, I had a bit of trouble:

1. xmldom is not in package.json
2. I did not know I needed to start mongo to run the app

I added xmldom to the package.json file, so it automatically installs with `npm install`.  I also added a `Procfile.local` file that starts both node and mongo using foreman.  Instructions were added to the README.