implement vagrant support

- just run vagrant up and wait some time
- you have a running coffeestats instance at http://localhost:8080/
  afterwards
- the port may be changed in Vagrantfile
- settings like database password can be changed in
  salt/roots/pillar/coffeestats.sls

see http://docs.vagrantup.com/v2/vagrantfile/index.html,
http://docs.vagrantup.com/v2/provisioning/salt.html and
http://docs.saltstack.com/ for reference