Fixed few typos

lib/active_model/serializer.rb

@@ -73,7 +73,7 @@ module ActiveModel
     class_attribute :perform_caching
 
     class << self
-      # set peform caching like root
+      # set perform caching like root
       def cached(value = true)
         self.perform_caching = value
       end

lib/generators/serializer/templates/serializer.rb

@@ -7,7 +7,7 @@ class <%= class_name %>Serializer < <%= parent_class_name %>
 <% if  generate_id_method %>
 
   # due to the difference between 1.8 and 1.9 with respect to #id and
-  # #object_id, we reccomend that if you wish to serialize id columns, you
+  # #object_id, we recommend that if you wish to serialize id columns, you
   # do this. Feel free to remove this if you don't feel that it's appropriate.
   #
   # For more: https://github.com/rails-api/active_model_serializers/issues/127

test/responder_test.rb

@@ -376,7 +376,7 @@ class ResponderTest < ActionController::TestCase
     assert_equal '{"awesome":[]}', @response.body
   end
 
-  def test_render_json_empty_arry_with_array_serializer_root_false
+  def test_render_json_empty_array_with_array_serializer_root_false
     ActiveModel::ArraySerializer.root = false
     get :render_json_empty_array
     assert_equal '[]', @response.body

test/serialization_test.rb

@@ -379,7 +379,7 @@ class RenderJsonTest < ActionController::TestCase
     assert_equal '{"awesome":[]}', @response.body
   end
 
-  def test_render_json_empty_arry_with_array_serializer_root_false
+  def test_render_json_empty_array_with_array_serializer_root_false
     ActiveModel::ArraySerializer.root = false
     get :render_json_empty_array
     assert_equal '[]', @response.body