formatOutputDynamicBytes = function (param) {
    var length = (new BigNumber(param.dynamicPart().slice(0, 64), 16)).toNumber() * 2;
    return '0x' + param.dynamicPart().substr(64, length);
}
Should be used to format output bytes

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