make sure there is a dependency on Gitlab::CurrentSettings is

This fixes an issue where the Rails autoload system would throw various `Unable to autoload constant` errors (such as `Unable to autoload constant EE::ProjectsHelper`) when using the autoload system (such with `spring` or `reload!` in the rails console.

This error was specifically ocurring in the EE code, however, it's seems reasonable to place the fix in CE as a general innoculation.

config/application.rb

@@ -11,6 +11,7 @@ module Gitlab
     require_dependency Rails.root.join('lib/gitlab/redis/queues')
     require_dependency Rails.root.join('lib/gitlab/redis/shared_state')
     require_dependency Rails.root.join('lib/gitlab/request_context')
+    require_dependency Rails.root.join('lib/gitlab/current_settings')
 
     # Settings in config/environments/* take precedence over those specified here.
     # Application configuration should go into files in config/initializers