Allow page_cache_directory to be set as a Pathname

For example, page_cache_directory = Rails.root.join("public/cache")
Signed-off-by: NSantiago Pastorino <santiago@wyeworks.com>

actionpack/lib/action_controller/caching/pages.rb

@@ -106,7 +106,7 @@ def page_cache_file(path, extension)
           end
 
           def page_cache_path(path, extension = nil)
-            page_cache_directory + page_cache_file(path, extension)
+            page_cache_directory.to_s + page_cache_file(path, extension)
           end
 
           def instrument_page_cache(name, path)

actionpack/test/controller/caching_test.rb

@@ -156,6 +156,17 @@ def test_page_caching_conditional_options
     assert_page_not_cached :ok
   end
 
+  def test_page_caching_directory_set_as_pathname
+    begin
+      ActionController::Base.page_cache_directory = Pathname.new(FILE_STORE_PATH)
+      get :ok
+      assert_response :ok
+      assert_page_cached :ok
+    ensure
+      ActionController::Base.page_cache_directory = FILE_STORE_PATH
+    end
+  end
+
   private
     def assert_page_cached(action, message = "#{action} should have been cached")
       assert page_cached?(action), message