Get deploy running on Heorku

The `assets:precompile` task wasn't running without the `rake-pipeline` gem so the /build directory would be empty after deploy.

* Add Ruby 2.0 to Gemfile
* Add rake-pipline to trigger the assets:precompile
* Add Unicorn web server
* Add Procfile for Heroku deploys

Minor changes:

* Add gitignore file
* Add config.rb so Middleman can build
* Add sample index page