WIP - Add handlebars template to allow nested pages to access root level assets

[ByronDDelpinal]

Addresses issue #24

Things done:

• Added a handlebars default helper to the template that allows nested pages to access root level assets. Previously, trying to link to a root level asset from a nested page required you to specify the relative URL yourself.
• Provided example usage of the helper in the template files.

How to use:

• When referencing anything from an href or src property in markup, wrap in with the nestedUrl helper like this:

<a href="{{nestedUrl 'index.html'}}">Home</a>
<img alt="" src="{{nestedUrl 'images/image.png'}}">