install only in classes (? and modules)
  def self.install
    Object.send :include, PrivatePlease::Tracking::Extension
    ^^^^^^
    TOO WIDE
  end


DSL
    - observe class methods too

Report :
    - option : show file and line number of good candidate definition
    - option : show code snippet around the good candidate
	- display list of methods that were never called
	- display candidates that are already private

Doc
	- write README