Add support for setting the ordering option.

As per http://puppetlabs.com/blog/introducing-manifest-ordered-resources it's possible to set the ordering to one of three modes:
* `title-hash`, the current default of Puppet;
* `manifest`, the default per Puppet 4;
* `random`, should be used for tests to catch ordering issues.

Though I would prefer to set the default to `random` as that is the most valuable setting for testing I'm afraid that will trip too many people up, especially with Puppet's default changing to `manifest` in Puppet 4
as per https://github.com/puppetlabs/puppet/commit/9962f4a872b8412d04f16fdfd9e77789d02f7e84