Use hostmanager as provisioner

[vStone]

Allows using hostmanager as a provisioner.
I needed this to make sure the hosts file was updated before running my provisioning scripts.

[smdahlen]

@vStone I like the concept. Question -- why did you provide the configuration option for a provider?

[vStone]

It seems more... complete. I hope that in the future we will be able to use provider = :all or something of the kind.
Note, it should be easy enough to strip out for now if you would prefer that.

[smdahlen]

@vStone At the moment, it appears a user will always have to specify the backing provider of the machine. I would prefer to stay consist with the action hook and command logic which looks for other active machines with the same backing provider of the current machine. If you wouldn't mind modifying your request (by removing the provider config option), I'll go ahead and merge.

Over the next few months, we can watch how Vagrant core evolves its support for providers.

[vStone]

This should do the trick.

[smdahlen]

Thanks. I will go ahead and bump the version and push out an updated gem.