Fix the CollectionProxy#new method

It was using the default Active Record implementation.

Fixes #21

lib/active_record/mass_assignment_security/associations.rb

@@ -54,6 +54,7 @@ class CollectionProxy
       def build(attributes = {}, options = {}, &block)
         @association.build(attributes, options, &block)
       end
+      alias_method :new, :build
 
       def create(attributes = {}, options = {}, &block)
         @association.create(attributes, options, &block)

test/attribute_sanitization_test.rb

@@ -595,6 +595,40 @@ def test_has_many_build_with_strict_sanitizer
     end
   end
 
+  # new
+
+  def test_has_many_build_with_attr_protected_attributes
+    best_friend = @person.best_friends.new(attributes_hash)
+    assert_default_attributes(best_friend)
+  end
+
+  def test_has_many_build_with_attr_accessible_attributes
+    best_friend = @person.best_friends.new(attributes_hash)
+    assert_default_attributes(best_friend)
+  end
+
+  def test_has_many_build_with_admin_role_with_attr_protected_attributes
+    best_friend = @person.best_friends.new(attributes_hash, :as => :admin)
+    assert_admin_attributes(best_friend)
+  end
+
+  def test_has_many_build_with_admin_role_with_attr_accessible_attributes
+    best_friend = @person.best_friends.new(attributes_hash, :as => :admin)
+    assert_admin_attributes(best_friend)
+  end
+
+  def test_has_many_build_without_protection
+    best_friend = @person.best_friends.new(attributes_hash, :without_protection => true)
+    assert_all_attributes(best_friend)
+  end
+
+  def test_has_many_build_with_strict_sanitizer
+    with_strict_sanitizer do
+      best_friend = @person.best_friends.new(attributes_hash.except(:id, :comments))
+      assert_equal @person.id, best_friend.best_friend_id
+    end
+  end
+
   # create
 
   def test_has_many_create_with_attr_protected_attributes