This example loads both Google Maps and a twitter feed (via its JSONP service - check console for returned feed data)
Google Maps loads many JS files asynchronously, so listening just to the first script load isn't enough to check if it is ready to be used,
another problem is that the regular gmaps script uses document.write,
so we need to pass a `callback` parameter to make it not use `document.write` and wait for the callback call.