New helper templateIs to allow dynamic classes based on template name

[adamauckland]

Ditches the first handlebars plugin for gulp-hb which gives more useful information like the file name. Docs https://www.npmjs.com/package/gulp-hb

Added a custom helpers to get the template file name.

Also added a custom helper to return a classname if the current file template is a specific name:

{{ templateIs @file "index.hbs" "active" }}

returns "active" if the current template is index.hbs. Returns nothing otherwise.

This can be added to a

<div class="  {{ templateIs @file "index.hbs" "active" }}   "> 

To show the active link in a nav.