Improve .mayoral-box UI

This commit does multiple atomic things. You know, like many of the best
commits from engineers who are too lazy to properly split up chunks of
work.

* Moves JS to bottom of <body>
* Removes assets/js/main.js, which didn't appear to be doing anything
* Removes database config comments in favor of the .env file to use with
  foreman
* The thing the commit title says (makes the whole mayoral-box
  clickable, and have some stats below each of them)
Add temporary disclaimer

So any internet travelers who stumble upon opendisclosure.io don't think
too much of the numbers until we're done!
Improve templating with content_for

It's one thing that is awesome in Rails templating - the ability to
shove arbitrary content around with content_for. Here, it will allow us
to DRY up our templates between the homepage and other app pages.
Improve README with foreman

Foreman can set the environment variable for DATABASE_URL automatically.
Huzzah!
Merge pull request #34 from ted27/master

Improve some minor things