Add guest_os_type options for puppet provisioner

[mprince]

Issue

closes #72

List of Changes Proposed

Add guest_os_type options for puppet provisioner

Testing Evidence

Example Script

from packerlicious import provisioner, Template

provisioners = [
    provisioner.PuppetMasterless(manifest_file="site.pp", guest_os_type="windows"),
    provisioner.PuppetServer(guest_os_type="unix")
]

t = Template()
t.add_provisioner(provisioners)

print(t.to_json())

Results

{
  "provisioners": [
    {
      "guest_os_type": "windows",
      "manifest_file": "site.pp",
      "type": "puppet-masterless"
    },
    {
      "guest_os_type": "unix",
      "type": "puppet-server"
    }
  ]
}

If the value provided is not in ["windows", "unix"] following error

ValueError: String must be one of following: unix, windows

[coveralls]

Coverage decreased (-0.04%) to 81.746% when pulling 215fe4c on mprince:issue72 into 43665de on mayn:master.

[coveralls]

Coverage increased (+0.2%) to 81.944% when pulling ebba443 on mprince:issue72 into 43665de on mayn:master.

[mayn]

LGTM