use "/" for repo keying
use "/" for repo keying

This avoids the conflict between such repositories as:

  * pivotal-cf/experimental-repo
  * pivotal-cf-experimental/repo

To our knowledge this was never a real conflict but is quite the
timebomb.

* Cleaned up the set code into its own type.

Signed-off-by: Can Berk Güder <ed1dfb86e8d469f3acf95218f1ef796e19057d0f@pivotal.io>

pivotal-cf/cred-alert,pivotal-cf/cred-alert