Add additional template paths

[jwir3]

It would be really nice if we could have multiple template paths. For our website, we have a design system that we bundle into a .gem file that includes our templates. After adding the gem to the project and exposing the directory, this works great. The problem comes when I want to use a template that isn't included in the gem, but is specific to the website itself.

It seems like it should be possible to specify a set of search paths for Stache that would allow it to utilize whichever template was found first in the search paths.