feat(partials): Parse function to (re)name partials.

[djaax]

We need more flexibility when it comes to naming partials and don't want to be constrained by our folder structure.

For example, we have

/components
    /button
        button.hbs
    /template
        otherTemplate.hbs

Currently, this names the partial button/button and template/otherTemplate.

This renaming function allows more flexibility, e.g., naming the two templates button and otherTemplate, ignoring the folder structure.

[UziTech]

All new development of express-handlebars is done on a new repo express-handlebars/express-handlebars. Please create a PR there.