Add shared integration test examples
Add purchase flow integration spec
Add Hashie gem
Add Application module, serving as global holder of config values
Selectively load files in spec setup
Use Application.config in place of CURRENCY_RATES constant
Move application loading to config.ru
Move db connection initialization to boot
Selectively load models in db rake tasks
Set up Rake tasks for running unit and integration tests
Disable enforcing locales
Add rake task for Pry