restful_authentication/tasks are deprecated

``` bash
alexandre$ rake db:migrate RAILS_ENV="development"
Please install RDoc 2.4.2+ to generate documentation.
DEPRECATION WARNING: Rake tasks in vendor/plugins/restful_authentication/tasks are deprecated. Use lib/tasks instead. (called from /var/lib/gems/1.8/gems/rails-2.3.18/lib/tasks/rails.rb:10)
...
```
