Fix notice caused by drops using pantheon project name instead of drupal

[skwashd]

This fixes issue #27 which is caused by drops using the pantheon project name instead of drupal. dpm() confirms the different project names.

Once I applied the patch the notice went away.

[joshkoenig]

Not sure this is the right answer. For portability we may well want to go back to using "drupal" in our core. I'll need to see why we changed that in the first place; it may be totally unnecessary.