click handler
@method pageview
@param {Object} payload payload object
@param {Object} payload.category category
@param {Object} payload.action action
@param {Object} payload.label label
@param {Function} calback callback function
function (payload, callback) {
                var i13nNode = payload.i13nNode;
                if (i13nNode) {
                    var model = i13nNode.getMergedModel();
                    var hitType = 'event';
                    var params = {
                        hitType: hitType,
                        eventCategory: model.category || DEFAULT_CATEGORY,
                        eventAction: model.action || DEFAULT_ACTION,
                        eventLabel: model.label || i13nNode.getText(payload.target) || DEFAULT_LABEL,
                        eventValue: model.value || DEFAULT_VALUE,
                        transport: model.transport || DEFAULT_TRANSPORT,
                        nonInteraction: model.nonInteraction || DEFAULT_NON_INTERACTION,
                        hitCallback: callback
                    };
                    _command.call(this, {
                        tracker: model.tracker || '',
                        commandName: 'send',
                        arguments: [
                            hitType,
                            params
                        ]
                    });
                } else {
                    callback && callback();
                }
            }