Create reduced versions of Orchestrator and Reporter

Since the guard-rubycritic gem does not need to generate a "Churn vs
Complexity" scatter plot or generate an index of analysed files, it
makes sense to create these smaller, guard-specific classes.

The Orchestrators were put inside a folder aptly named "orchestrators".
The Reporters were put inside a folder aptly named "reporters".

I don't like the fact that Orchestrator now has another two instance
variables, but maybe that is alright.
Rename ReportGenerators
Bump to 0.0.13