Added Debian and Ubuntu boxes and Ansible provision.

Hi,

I wanted to test psdash in a Debian box, so I ended up adding Debian and Ubuntu boxes (from Chef's Bento project) and Ansible provision. I took the liberty to assume that your "chef/centos-6.5" box also came from that same project and added the respective URL. Hope that's ok! :)

Vagrantfile:
- Added 'boxes' dict with Debian, Ubuntu and CentOS boxes configs;
- Using private addresses on VMs so we no longer need
  port-forwarding, which would complicate maintaining multiple VMs
  for testing;
- Using Ansible for provisioning.

psdash.yml:
- Simple Ansible playbook that installs psdash and its dependencies
  in Red Hat and Debian bases OS.

.gitignore:
- Added vagrant artifacts.