    function addBeneficiary (
        address account,
        uint256 start,
        uint256 duration,
        uint256 cliff,
        uint256 amount
    ) public {
        require(amount != 0 && start != 0 && account != address(0x0) && cliff < duration && beneficiary[account].start == 0);
        require(token.transferFrom(msg.sender, address(this), amount));
        beneficiary[account] = Beneficiary({
            start: start,
            duration: duration,
            cliff: start.add(cliff),
            totalAmount: amount,
            releasedAmount: 0
        });
    }