Fix namespace error in engine initialize.

lib/feeds/engine.rb

@@ -5,9 +5,9 @@ module Feeds
         gem_root = Feeds::Engine.root
         if ENV['worker_num']=='0' && File.basename($0) != 'rake' && !Rails.const_defined?('Console')
           require File.join(gem_root, 'app/models/site_feed_setting')
-          if defined?(SiteFeedSetting)
-            if SiteFeedSetting.count==0
-              SiteFeedSetting.create
+          if defined?(::SiteFeedSetting)
+            if ::SiteFeedSetting.count==0
+              ::SiteFeedSetting.create
             end
           end
 
@@ -26,7 +26,7 @@ module Feeds
           authorizable
           if File.basename($0) != 'rake'
             begin
-              avoid_page_cache SiteFeed
+              avoid_page_cache ::SiteFeed
             rescue => e
               puts ["avoid_page_cache", e.to_s]
             end