Add support to customize Parallels Vagrantfile

- convert key from snake_case to dash-case (prevents ugly yaml using
  quoted keys)
- the customize hash below should be considered as a default to allow one to
  close the vm window if Parallels Desktop is open:

```yaml
- name: parallels-vm
  driver:
    provider: parallels
    box: parallels/centos-65
    customize:
      on_window_close: keep-running
```

converts to:

```ruby
  c.vm.provider :parallels do |p|
    p.customize ["set", :id, "--on-window-close", "keep-running"]
  end
```
Add SSH ProxyCommand to state if present
Support box_version option
Qualify VM names with cookbook name

VirtualBox names VMs after the base name of the current directory, which
results in names like default-centos-65_default_..., which are not very
helpful when looking at a process list or working in the VirtualBox GUI,
especially when working with several cookbooks at once.

Change the working directory name created by kitchen-vagrant to look
like

    kitchen-${cookbook}-${rest as before}

to make things clearer.  (${cookbook} is actually just the name of the
root directory for Test Kitchen, but that's usually a cookbook name.)
Use correct urls to download vagrant
add libvirt to vagrant template.
vagrant-libvirt needs memory to be a integer.
Add box_check_update option
Do not use FQDN as default machine hostname

Since vagrant 1.6.4 vagrant fails to setup windows guest with FQDN as hostname.
Vagrant config password (Not Vagrant recommended)
Added ssh config
Add support for generating vm.communicator so winrm can be specified.
Add configuration option for user Vagrantfiles
Fix indentation error
Simplify sourcing of Vagrantfiles
Update README with config option
Remove review comment
Make box_url optional

Vagrant 1.5 doesn’t need it anymore, just the name from the Vagrant cloud