fix(controller/registry): strip hostname from repo

The changes to the registry module did not strip the hostname from the
app image. This fixes that by properly parsing the source for the
repository name in the registry and the tag.
Merge pull request #1500 from deis/hotfix-registry-module

fix(controller/registry): strip hostname from repo
docs(*): make OpDemand the maintainer

OpDemand collectively maintains the images. It's a group effort :)