Fix Gemfile and controller spec to enable Guard testing

(avoid testing errors by Kaminari)
Fix organization validation duplication
Fix Guardfile to reload FactoryGirl file when edited
Add activities controller spec

Delete needless request spec (We don't use models_path in view)

Conflicts:
	app/controllers/api/v1/activities_controller.rb
	app/models/activity.rb
Add scopes in activity model

Fix activity controller to use scopes

Conflicts:
	app/controllers/api/v1/activities_controller.rb
Merge pull request #43 from Mura-Mi/develop-activities

Develop activities