Make SmellAdapters initialize their respective Analysers
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.)
Add Flog QualityAdapter
Add Overview page
Create Turbulence class

This class is responsible for gathering churn and complexity data so it
can be rendered in a scatter plot by a js chart library.
Create "Churn vs Complexity" scatter plot

Probably the most useful feature of this gem. The problems I'm feeling
while developing this gem can already be gleaned just by analysing the
scatter plot of this gem's codebase:

* The Reporter class is getting unmanageable.

* A SourceControlSystem instance is always being passed around from
class to class. Should it be some kind of global singleton object? I'm
tempted to put it inside the Configuration class, but that doesn't feel
right.