Pillar data export

I wanted an easy way to pass data from my Vagrantfile into pillar so I created my own custom plugin at one point.  I rewrote the code with several improvements and integrated it into salty-vagrant because it just seemed like it belongs here.  There is a __pillar_root__ option to specify the path to your pillar root and usage is pretty simple:

    config.vm.provision :salt do |salt|
      salt.pillar(:hosts, {
        "hostnames" => {
          "www" => "www.example.com",
          "intranet" => "intranet.example.com"
        }
      })

      salt.run_highstate = true
    end

This will create the file _{pillar_root}_ __/_gen/hosts.sls__ with the following contents:

    hostnames:
      www: www.example.com
      intranet: intranet.example.com

Additionally, _{pillar_root}_ __/top.sls__ will be modified so that it pulls in the generated file:

    base:
      '*':
        - _gen/hosts

I welcome any and all constructive feedback and would love to see this incorporated in the next released version or so.  If there would be a better way to implement any of this or some use cases I need to consider please discuss.