Update Modulefile

Updates name to try and fix puppet-librarian error:
Not a valid full name: drush
Adds option to use this module without dependencies.

Squashed commit of the following:

commit f747d0b51c6342da537e6e22a4a9447681e6c92c
Author: Florian Weber <f.weber@digi-info.de>
Date:   Fri Jan 18 19:48:44 2013 +0100

    Adds option to use this module without dependencies.