You have to add the deepmodules gem

http://github.com/morhekil/capistrano-deepmodules/tree/master

$ gem sources -a http://gems.github.com
$ sudo gem install morhekil-capistrano-deepmodules

and add 

require 'capistrano/deepmodules'
 
to the top of ypur Capfile

and 

Dir['vendor/extensions/capistrano/lib/recipes/*.rb'].each { |plugin| load(plugin) } 

to the bottom of your Capfile