Merge pull request #61 from frankban/external-mgosuite

Use the external MgoSuite.

Mostly mechanical.
Remove the testing/mgo* bits which are now in github.com/juju/testing.
Add testing.Certs to be used when registering the MgoSuite tests.
Merge branch 'master' of https://github.com/juju/juju
envions/configstore: Storage.List()

Add the List() method to the Storage interface. List lists all
the existing environments in storage.
Merge pull request #35 from waigani/list-store-interface

envions/configstore: Storage.List()

Add the List() method to the Storage interface. List lists all
the existing environments in storage.