Login to your Pantheon.io account (2 free sandbox sites with your login account).
Then go to:
Give your site a name (this will create a dev-yourname.patheon site)
Then when the environment is ready, click on Install Drupal
There is a notice that CviCRM needs to be installed -- this is one more click (all green to install) that will set up CiviCRM and then install Drupal.
Have a cup of tea while the rest of the installer runs.
Fill in your site name, user1 name and password and click save.
Boom! You're taken to the CviCRM Startup Configuration page.
Note: On Dec. 22 CiviCRM was v 4.7.27