Add method to Template to retrieve list of registered templates

[mojavelinux]

Add a method to the Opal Template class that provides access to the list of registered templates. Currently, there is no way to know what got registered, which could be convenient for rendering a template in response to some sort of request.

Here's a suggestion for the API:

def paths
  @_cache.keys
end

[adambeynon]

@mojavelinux Yeah, sounds fine to me. If you open a pull request I will merge it in, or I can add it later (tomorrow?) once I finish on reworking compiler nodes.

[adambeynon]

That commit implements the method. paths seems the best choice of name as well.

[mojavelinux]

Yea ha! Thanks!