convert Rails 4.x engine to Rails 3.x application

Switching over to a Rails app instead of building an engine will make prototyping go faster. Also, the current [Brigade](https://github.com/codeforamerica/brigade/) repo is a Rails 3.x app, so using Rails 3.x instead of Rails 4.x should make any possible adoption easier.
add authorization, config support

authorization includes omniauth support for github, facebook, and twitter
add support for creating user based on auth, if user isn't yet complete

This will be the case if a provider doesn't supply an email (e.g., Twitter); in this case, we still want to allow the user to create an account, as well as associate that account with the provider, so that future logins will work

User should also be confirmable if this is the case