formatOutputString = function (param) {
    var length = (new BigNumber(param.dynamicPart().slice(0, 64), 16)).toNumber() * 2;
    return utils.toUtf8(param.dynamicPart().substr(64, length));
}
Should be used to format output string

@method formatOutputString
@param {SolidityParam} left-aligned hex representation of string
@returns {String} ascii string