remove Rails 3 documentation and add for Rails 4 support only
remove Rails 3 documentation and add for Rails 4 support only

ehannes/fullcalendar-rails-engine,rikkipitt/fullcalendar-rails-engine,ehannes/fullcalendar-rails-engine,ehannes/fullcalendar-rails-engine,rikkipitt/fullcalendar-rails-engine,vinsol/fullcalendar-rails-engine,vinsol/fullcalendar-rails-engine