Add spec/dummy/db/schema.rb

- bundle exec rake app:db:migrate
- git add spec/dummy/db/schema.rb

`bundle exec rake` will failure if spec/dummy/db/schema.rb is not exists:

```
$ bundle exec rake
/home/travis/build/hanachin/remote_factory_girl_home_rails/spec/dummy/db/schema.rb
doesn't exist yet. Run `rake db:migrate` to create it, then try
again. If you do not intend to use a database, you should instead alter
/home/travis/build/hanachin/remote_factory_girl_home_rails/spec/dummy/config/application.rb
to limit the frameworks that will be loaded.
```