[#62831904] Replace built-in Puppet provider

Reuses code from the development VM to run Puppet using the puppet-apply
shell script rather than Vagrant's built-in Puppet provisioner.

Benefits
------

- Fixes issues when mounting synchronised folders under Vagrant 1.4.0.
- Uses `RBENV` to set the correct Ruby version.
- Provides a unified way to run `puppet apply`.
- Filters noisy storeconfigs warnings.
Merge pull request #12 from alphagov/62831904-vagrant-provisioning

[#62831904] Replace built-in Puppet provider