How to highlight a day which has an event in FullCalendar.js?

I am using FullCalendar.js in my website. I have set events from backend. I want to change look of the day which has an event. In other words I need some sort of class where I have "fc-day" and an event in it.

My code looks like and you see it on jsFiddle:

$('#calendar').fullCalendar({
    events: [{
        title: 'event1',
        start: '2013-01-01'
    }, {
        title: 'event2',
        start: '2013-12-05',
        end: '2013-12-07'
    }, {
        title: 'event3',
        start: '2013-12-15'
    }]
})