Take advantage of latest Handlebars features

[ericf]

There have been lots of interesting features added to Handlebars over the last few minor version releases. I think that we can use these newer features to handle some of the harder aspects of this package:

https://github.com/wycats/handlebars.js/blob/master/release-notes.md

[ericf]

The simplified refactor now uses options.data which persists down to all helpers and partials.