merge drush cookbook into deploy-drupal

[amirkdv]

The drush cookbook we are currently using is very small (20 loc). It should be merged with deploy-drupal and removed from dependencies.

[patcon]

Sorry for barging into this queue, but couldn't find any easy means to reach out (no Twitters?! :)

I like how to write cookbooks and run your issue queues! Any thoughts on helping out with the proviso project?
https://github.com/proviso/proviso/wiki/Design-Goals-DRAFT

(Feel free to tweet me to move out of this queue.)