Check for Rails 3 features
Check for Rails 3 features

Check for ::Rails::Engine when deciding whether to use the Rails 3 code.
This allows projects running Rails 2 + Sprockets to still use handlebars_assets.

cgvarela/handlebars_assets,leshill/handlebars_assets,jacquescrocker/handlebars_assets,envato/handlebars_assets,jacquescrocker/handlebars_assets,cgvarela/handlebars_assets,tjgrathwell/handlebars_assets,tjgrathwell/handlebars_assets,wideopenspaces/handlebars_assets,railsjedi/handlebars_assets,railsjedi/handlebars_assets,ksteigerwald/handlebars_assets,wideopenspaces/handlebars_assets,ksteigerwald/handlebars_assets,leshill/handlebars_assets,envato/handlebars_assets