[ADDED] custom template path functionallity with parameter

[Timu57]

I think many other people need to make their custom templates too, so I decided to make a pull request :)

[Roshyo]

Thanks for your contribution, but in order to not duplicate informations, we'd rather let knp snappy document wkhtmltopdf configuration. For the overriding part, I believe it's not required to add a template path. You simply need to create a file under app/Resources/BeHappySyliusInvoicePlugin/views/Invoice/pdf.html.twig

[Timu57]

Your right, my fault.. but I think you should update the README a little bit to make the setup easier.

At least, you should mention, that wkhtmltopdf is needed on the system.

[Roshyo]

Done.