database.yml

defaults: &defaults
  adapter: postgresql
  encoding: utf8
  reconnect: true
  min_messages: warning
  pool: 15
  timeout: 5000
  host: localhost
  
development:
  <<: *defaults
  database: site_development
  username: site
  password: site

test:
  <<: *defaults
  database: site_test
  username: site
  password: site

production:
  <<: *defaults
  database: site_production
  username: site
  password: site

Gemfile

gem 'pg', '>= 0.12.0'