Remove SmellsAggregator class

That logic rightfully belongs to the AnalysersRunner class
Rename variables
Rename test folder and files
Add Flog QualityAdapter
Add Churn class

It's so simple to calculate churn, there's really no need to depend on
the churn gem.
(For now. If there ever is a need to calculate churn in other source
control systems, maybe it would be better to use that gem.)