[Radiant] [ANN] Ray extension

[john muhl]

Just a note that Ray is no longer “sort of stupid about migrate/update  
tasks”. Now an effort is made to determine whether there are any tasks.

If a `vendor/extensions/extension_name/lib/tasks/ 
extension_name_extension_tasks.rake` file is found, Ray takes a peek  
inside to determine whether there are migrate and update tasks and  
only runs tasks that it actually finds.

If no `vendor/extensions/extension_name/lib/tasks/ 
extension_name_extension_tasks.rake` file is found the entire post  
install process is skipped.

The changes are available on GitHub.