Update script to work with Ubuntu 13.04 / Ruby 2.0.0 combo.
Update script to work with Ubuntu 13.04 / Ruby 2.0.0 combo.

  * Update library dependencies for Ubuntu 13.04 / Ruby 2.0.0-p0

  * Use latest RVM install procedure.

  * Use Ruby 2.0.0 patchlevel 0.

  * Change cURL output mode.

  * Change Heroku toolbelt installation procedure.

etrepat/devstrap