Don't force translations for the current locale

Globalize creates a translation for the current locale, and the only way
I've found to change this behaviour is to monkey-patch it.

The original code uses `translation.locale` instead of
`Globalize.locale`. Since `translation.locale` loads the translation
with empty attributes. It both makes the record invalid if there are
validations and it makes it almost impossible to create a record with
translations which don't include the current locale.

See also the following convertations:

https://github.com/globalize/globalize/pull/328
https://github.com/globalize/globalize/issues/468
https://github.com/globalize/globalize/pull/578
https://github.com/shioyama/mobility/wiki/Migrating-from-Globalize#blank-translations

config/initializers/globalize.rb

@@ -0,0 +1,13 @@
+module Globalize
+  module ActiveRecord
+    module InstanceMethods
+      def save(*)
+        # Credit for this code belongs to Jack Tomaszewski:
+        # https://github.com/globalize/globalize/pull/578
+        Globalize.with_locale(Globalize.locale || I18n.default_locale) do
+          super
+        end
+      end
+    end
+  end
+end