Use symbols for action hook names

Rails 5 requires symbols for the names of hooks. This fixes the
following deprecation warning:

> DEPRECATION WARNING: Passing string to define callback is deprecated
> and will be removed in Rails 5.1 without replacement. (called from
> verify_scoped_resource at lib/kracken/controllers/json_api_compatible.rb:69)

Author: cupakromer

lib/kracken/controllers/json_api_compatible.rb

@@ -50,7 +50,7 @@ def munge_resource_root!
         end
 
         def verify_scoped_resource(resource, options = {})
-          name = "verify_scoped_#{resource}"
+          name = "verify_scoped_#{resource}".to_sym
           relation = options.extract!(:as).fetch(:as, resource).to_s.pluralize
           scope = options.extract!(:scope).fetch(:scope, :current_user)
           resource_id = (resource_type == resource.to_sym) ? :id : "#{resource}_id"