Fix #34

As long as we need to pre-provision floating IP and specify it
in the Vagrantfile there's no need to request Nova or Neutron
to get a public IP address for SSH. Just get it from configuration.
Read service endpoints from keystone authentication response
Add rubocop to CI process
Rubocop config
Fix some rubocop offenses
update appraisal conf

Fix #32
Refactor Openstack client
Make rubocop happy
Fix typo in error message placeholder