function release() onlyOwner public {
        uint toRelease = calculateVestedAmount().sub(released);
        uint left = token.balanceOf(this);
        if (left < toRelease) {
            toRelease = left;
        }
        require(toRelease > 0, "nothing to release");
        released = released.add(toRelease);
        require(token.transfer(msg.sender, toRelease));
        emit Released(toRelease);
    }