Task: Heroku background worker to Open States APIs

[kwhinnery]

We'd like to poll the Open States API on a regular interval in order to send out relevant notifications to subscribers. The target deployment environment for this application is Heroku. We should configure a Procfile and a Node module (put a placeholder here) that will run in a worker dyno on Heroku to poll the APIs. Let's get this in place, and we can tweak the behavior later.

Acceptance criteria

• Create a function that will execute as a background task on Heroku
• Create Procfile configuration as necessary
• Create test for the background function (placeholder is fine for now)

[jefflinwood]

Suggestion: Use the Heroku Scheduler instead of a custom schedule process. That way, it won't need to be scaled up to a separate dyno, and there doesn't need to be an entry in the Procfile. I think all that's needed is a new script in package.json. Will test, and make a PR.