Adding option to specify asset server, filter followers query by local accounts

during Fan Out On Write to load less stuff into memory

config/environments/production.rb

@@ -13,6 +13,7 @@ Rails.application.configure do
   # Full error reports are disabled and caching is turned on.
   config.consider_all_requests_local       = false
   config.action_controller.perform_caching = true
+  config.action_controller.asset_host      = ENV['CDN_HOST']
 
   # Disable serving static files from the `/public` folder by default since
   # Apache or NGINX already handles this.