Iterates through all elements in iterator.  @note Delegates to it's values `forEach` method.
@param callback {Function}
@param context {Object}
@method sjl.stdlib.ObjectIterator#forEach
@returns {sjl.stdlib.Iterator}
function (callback, context) {
            var self = this,
                values = self._values;
            context = context || self;
            self._keys.forEach(function (key, index, keys) {
                callback.call(context, values[index], key, keys);
            });
            return this;
        }