formatInputInt = function (value) {
    BigNumber.config(c.ETH_BIGNUMBER_ROUNDING_MODE);
    var result = utils.padLeft(utils.toTwosComplement(value).toString(16), 64);
    return new SolidityParam(result);
}
Formats input value to byte representation of int
If value is negative, return it's two's complement
If the value is floating point, round it down

@method formatInputInt
@param {String|Number|BigNumber} value that needs to be formatted
@returns {SolidityParam}