fixes #165 avoid overwriting AR::Base inherited method

Kaminari can now coexist with other gems that defines `inherited`

lib/kaminari/models/active_record_extension.rb

@@ -5,9 +5,12 @@ module Kaminari
     extend ActiveSupport::Concern
     included do
       # Future subclasses will pick up the model extension
-      def self.inherited(kls) #:nodoc:
-        super
-        kls.send(:include, Kaminari::ActiveRecordModelExtension) if kls.superclass == ActiveRecord::Base
+      class << self
+        def inherited_with_kaminari(kls) #:nodoc:
+          inherited_without_kaminari kls
+          kls.send(:include, Kaminari::ActiveRecordModelExtension) if kls.superclass == ActiveRecord::Base
+        end
+        alias_method_chain :inherited, :kaminari
       end
 
       # Existing subclasses pick up the model extension as well