Fix extra subdirectories appearing in category links and atom.xml link.

plugins/category_generator.rb

@@ -104,9 +104,8 @@ module Jekyll
     #
     def category_links(categories)
       dir = @context.registers[:site].config['category_dir']
-      root_url = @context.registers[:site].config['root'].sub(/\/$/, '')
       categories = categories.sort!.map do |item|
-        "<a class='category' href='#{root_url}/#{dir}/#{item.gsub(/_|\W/, '-')}/'>#{item}</a>"
+        "<a class='category' href='/#{dir}/#{item.gsub(/_|\W/, '-')}/'>#{item}</a>"
       end
 
       case categories.length