Add EPP & ruby parser validate/syntax check

[ghost]

• add EPP (Puppet 4.x templates) via puppet epp validate
• add Ruby syntax checking (ruby -c); useful for type/provider/custom facts in module development

I added these few additional checks for our implementation, since we started with Puppet 4.7 and did a bit of type/provider work with Puppet. It's useful to catch Ruby syntax problems at precommit

Let me know if there's any issues adding this in or if you'd rather keep this out of the original repo :)

[mattiasgeniar]

Nice, thank you for this PR!