Update Rakefile to db:migrate
Rename config/database.yml
Add migration file
Add models
Merge remote-tracking branch 'origin/master' into feature-add-activerecord
Small fix
Update Rakefile to drop db
Fix spec_helper
Fix test
Add test file about Todo model
Merge pull request #21 from junsumida/feature-add-activerecord

ActiveRecordを使うようにするなど