Stups-pierone

Merge pull request 94 from zalando-stups/check-credhelper

Check that the credential helper is available on the PATH

Merge pull request 93 from zalando-stups/cred-helper

Implement a proper credentials helper

Merge pull request 85 from zalando-stups/support-teams-with-underscores

validators.py: allow team names to contain underscores

Merge pull request 84 from zalando-stups/sunset-trusted

Sunset all support related to `trusted` flag

Fix 'pierone login' on Mac (82)

Docker for Mac uses the Keychain credentials helper by default, which causes the auth token to be ignored. There was an attempt at fixing it by deleting the `credsStore` key, but the actual key is called `credSstore` ¯\\\_(ツ)\_/¯.
Instead of removing stuff from the user's Docker config, just configure the URL to not use a credentials helper explicitly.

Fix status display (80)

* Fix Status Reason in pierone tags
CLI expected ``status_reason_summary`` but the key is called
``status_reason``.

* Make status in pierone describe be the same as returned by API