fix(client): KeyError on cookie retrieval

Fixed an issue where 'no active controller' message didn't show if
cookies didn't already exist.

client/deis.py

@@ -368,7 +368,7 @@ def _dispatch(self, method, path, body=None,
         Dispatch an API request to the active Deis controller
         """
         func = getattr(self._session, method.lower())
-        controller = self._settings['controller']
+        controller = self._settings.get('controller')
         if not controller:
             raise EnvironmentError(
                 'No active controller. Use `deis login` or `deis register` to get started.')