Fix gravatar helpers loading (closes #207)

config/environments/development.rb

@@ -36,4 +36,4 @@ Rails.application.configure do
   # config.action_view.raise_on_missing_translations = true
 end
 
-AvatarHelper.include(AvatarHelper::GravatarURL)
+AvatarHelper.send(:include, AvatarHelper::GravatarURL)

config/environments/production.rb

@@ -77,4 +77,4 @@ Rails.application.configure do
   config.active_record.dump_schema_after_migration = false
 end
 
-AvatarHelper.include(AvatarHelper::GravatarURL)
+AvatarHelper.send(:include, AvatarHelper::GravatarURL)

config/environments/test.rb

@@ -38,4 +38,4 @@ Rails.application.configure do
   # config.action_view.raise_on_missing_translations = true
 end
 
-AvatarHelper.include(AvatarHelper::TestAvatarURL)
+AvatarHelper.send(:include, AvatarHelper::TestAvatarURL)