Add :es => :en locale fallback for translatable resources

The application default_locale is :es, while most seed data
is created in English. This means that translatable resources
might only have English translations. This change is so that,
when the locale is set to Spanish, the English translations
are shown instead of empty content.

config/initializers/globalize.rb

@@ -0,0 +1 @@
+Globalize.fallbacks = {es: [:es, :en]}