Use group :all

- allows for precompiling and on-the-fly (dev usually)

lib/handlebars_assets/engine.rb

@@ -1,6 +1,6 @@
 module HandlebarsAssets
   class Engine < ::Rails::Engine
-    initializer "sprockets.handlebars", :after => "sprockets.environment", :group => :assets do |app|
+    initializer "sprockets.handlebars", :after => "sprockets.environment", :group => :all do |app|
       next unless app.assets
       app.assets.register_engine('.hbs', TiltHandlebars)
     end