Be able to use a Google calendar as source

On xwiki.org we have a page called Events where we display an external calendar, see http://www.xwiki.org/xwiki/bin/view/Main/Events

This page used to work on older version, so it can be caused by the xwiki.org update to 5.4, the update to app version 1.1.5 or because Google changed the feed format.

Currently having

{{calendar json="https://www.google.com/calendar/feeds/committers%40xwiki.org/public/basic" editable="false"  year="2014" /}}

doesn't display any result.

The calendar entries are available at https://www.google.com/calendar/embed?src=committers%40xwiki.org