Add tests for Handlebars.prototype methods

* processTemplate
* processTemplateGetFragment
* getTemplate

Change-Id: I3386bbdd7bdcbcdfc46d2416d50678bc50df898b
Add tests for Handlebars.prototype.callHelper

Add missing documentation

Change-Id: Ib3c1756b9504ae6ba4a4455b829f64854f7684b4
Merge "Add tests for Handlebars.prototype methods"
Merge "Add tests for Handlebars.prototype.callHelper"