testing setup: rspec for integration tests
dependencies setup: pessimisitic versions
scaffold: DataVolume

```
bundle exec rails g scaffold data_volume hospital_id:integer year:integer
admissions_count:integer diagnoses_coun
t:integer procedures_count:integer diagnosis_deceased_count:integer
procedure_deceased_count:integer read
mission_count:integer diagnosis_llos_count:integer
procedure_llos_count:integer diagnosis_death_expected:
float procedure_death_expected:float
diagnosis_readmission_expected:float procedure_readmission_expected:
float diagnosis_llos_expected:float procedure_llos_expected:float
```