Changing from SQLite to Postgres & clone_to_local

This commit adds support for both Postgres locally, as well as a neat
Rake task which aids in cloning data from production to your local
machine. In the event that you need to install Postgres for the first
time, I'd recommend that you follow the instructions that are listed
here:

http://listenin.gs/2014/07/17/installing-postgres-for-the-first-time/

After that, you'll be able to get production data onto your machine by
running:

```
rake db:production:clone_to_local
```