Returns the permission granted value.

@function
@memberof! webNotification
@private
@returns {Boolean} True if permission is granted, else false
function getPermission() {
            var permission = NotificationAPI.permission;

            /**
             * True if permission is granted, else false.
             *
             * @memberof! webNotification
             * @alias webNotification.permissionGranted
             * @public
             */
            var permissionGranted = false;
            if (permission === 'granted') {
                permissionGranted = true;
            }

            return permissionGranted;
        }