Fix %d should be %s according to govet
Allow use of dashes in keys

You could have a key such as /prefix/your-key which should be
normalized to your_key since we cannot use - in go templates.
Support for reusing templates in various resources

I've got one usecase, generating nginx configs for different apps that
will share a configuration template.

This allows to generate such configuration with per-resource prefixes.
See an example in docs/templates-scoped-resources.md