Adding cache support to version 0.10.0

It's a new implementation of cache based on ActiveSupport::Cache.
The implementation abstracts the cache in Adapter class on a
private method called cached_object, this method is intended
to be used on Adapters inside serializable_hash method in order
to cache each instance of the object that will be returned by
the serializer.

Some of its features are:
- A different syntax. (no longer need the cache_key method).
- An options argument that have the same arguments of ActiveSupport::Cache::Store, plus a key option that will be the prefix of the object cache on a pattern "#{key}-#{object.id}".
- It cache the objects individually and not the whole Serializer return, re-using it in different requests (as a show and a index method for example.)

test/test_helper.rb

@@ -1,13 +1,21 @@
-require "bundler/setup"
+require 'bundler/setup'
 
 require 'rails'
 require 'action_controller'
 require 'action_controller/test_case'
-require "active_support/json"
+require 'action_controller/railtie'
+require 'active_support/json'
 require 'minitest/autorun'
 # Ensure backward compatibility with Minitest 4
 Minitest::Test = MiniTest::Unit::TestCase unless defined?(Minitest::Test)
 
+class Foo < Rails::Application
+  if Rails.version.to_s.start_with? '4'
+    config.action_controller.perform_caching = true
+    ActionController::Base.cache_store = :memory_store
+  end
+end
+
 require "active_model_serializers"
 
 require 'fixtures/poro'