Prevent deprecation warning in Rails 4.0

Use `all` instead of `scoped` if possible. Closes #484

lib/draper/decoratable.rb

@@ -53,7 +53,8 @@ module Draper
       # @param [Hash] options
       #   see {Decorator.decorate_collection}.
       def decorate(options = {})
-        decorator_class(options[:namespace]).decorate_collection(scoped, options.reverse_merge(with: nil))
+        collection = Rails::VERSION::MAJOR >= 4 ? all : scoped
+        decorator_class(options[:namespace]).decorate_collection(collection, options.reverse_merge(with: nil))
       end
 
       # Infers the decorator class to be used by {Decoratable#decorate} (e.g.

spec/draper/decoratable_spec.rb

@@ -108,9 +108,11 @@ module Draper
     end
 
     describe ".decorate" do
+      let(:scoping_method) { Rails::VERSION::MAJOR >= 4 ? :all : :scoped }
+
       it "calls #decorate_collection on .decorator_class" do
         scoped = [Product.new]
-        Product.stub scoped: scoped
+        Product.stub scoping_method => scoped
 
         Product.decorator_class.should_receive(:decorate_collection).with(scoped, with: nil).and_return(:decorated_collection)
         expect(Product.decorate).to be :decorated_collection
@@ -118,7 +120,7 @@ module Draper
 
       it "accepts options" do
         options = {with: ProductDecorator, context: {some: "context"}}
-        Product.stub scoped: []
+        Product.stub scoping_method => []
 
         Product.decorator_class.should_receive(:decorate_collection).with([], options)
         Product.decorate(options)

spec/spec_helper.rb

@@ -1,5 +1,6 @@
 require 'bundler/setup'
 require 'draper'
+require 'rails/version'
 require 'action_controller'
 require 'action_controller/test_case'