[React] React Fundamentals: Add-on ClassSet() for ClassName

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    var BHeart =
            React.createClass({
                render:function(){
                    var cx = React.addons.classSet;
                    var classes = cx({
                        'glyphicon': true,
                        'glyphicon-heart': true
                    });
                    return <span className={classes}></span>
                }
            });