fix(client): remove check for error message

This check was originally used for API/client version mismatches, but
breaks when the response is not as to be expected. The client response
works, anyways:

    ><> deis apps
    405 METHOD NOT ALLOWED
    {u'error': u'Client and server versions do not match.\nClient version: 0.10\nServer version: 0.11'}

closes #1448