Convenience script to set up an sbuild environment for Debian Developers

 Run "sudo sbuild-debian-developer-setup" to add the current user to the sbuild
 group, create an schroot for building packages for Debian unstable, and create
 a cronjob which updates said schroot daily.
 .
 This script assumes you are on an un-metered internet connection (daily schroot
 updates might be costly otherwise).