Fix statisticable concern definition

Methods defined inside "included" cannot be called using `super` from
a class including the module.

app/models/concerns/statisticable.rb

@@ -4,6 +4,7 @@ module Statisticable
 
   included do
     attr_reader :resource
+  end
 
   def initialize(resource)
     @resource = resource
@@ -145,7 +146,6 @@ module Statisticable
         I18n.t("stats.age_range", start: start, finish: finish)
       end
     end
-  end
 
   class_methods do
     def stats_methods