Add grape routing print

Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>

lib/tasks/grape.rake

+namespace :grape do
+  desc 'Print compiled grape routes'
+  task routes: :environment do
+    API::API.routes.each do |route|
+      puts route
+    end
+  end
+end