Replacing the version check with the function call

lib/simple_navigation/adapters/rails.rb

@@ -82,7 +82,7 @@ def extract_controller_from(context)
 end
 
 # Initializer for Rails3
-if defined?(Rails) && Rails::VERSION::MAJOR == 3
+if defined?(Rails) && SimpleNavigation::Adapters::Rails.gte_rails3?
   module SimpleNavigation                                                                                                
     class Railtie < Rails::Railtie                                                                                       
       initializer "simple_navigation.register" do |app|