Add sidekiq 5 version support

Author: constXife

lib/redmine_sidekiq/configure.rb

@@ -1,5 +1,10 @@
 require 'sidekiq'
 
+# Enable extensions if sidekiq version > 4
+if Sidekiq::Extensions.respond_to?(:enable_delay!)
+  Sidekiq::Extensions.enable_delay!
+end
+
 module RedmineSidekiq
   class Configure
     file = File.join(Rails.root, 'plugins/redmine_sidekiq/config/sidekiq.yml')