Fix Model::Base#attributes to use symbols as key at final example
Fix Model::Base#save_on_insert to remove id from attributes of insertion at final example
Add PostgreSQL driver for final example
Trivia: indicate on Vagrant box name the exercise
Fix 'config/app' of final example wich was ignoring the environment configuration (hardcoded development)
Force 'test' environment at test.rb for the final example
Alter default config of last example to run tests using sqlite3 and development in PostgreSQL
Copy a Vagrantfile to final example