check in modifier (canBeStoredWith128Bits)

[pauliax]

The check in this modifier should be "<="

modifier canBeStoredWith128Bits(uint256 _value) {
    require(_value < 340282366920938463463374607431768211455);
    _;
}

because 128 bits can hold a maximum of 2^128-1 which is equal to 340282366920938463463374607431768211455 so it makes sense (according to the modifier's name) to have a "<=" instead of "<".

by the way, here everything is fine:
modifier canBeStoredWith64Bits(uint256 _value) {
require(_value <= 18446744073709551615);
_;
}

[pauliax]

    // sanity check to ensure we don't overflow arithmetic (this big number is 2^128-1).
    require(avePrice < 340282366920938463463374607431768211455);

Same here (KittyMinting.sol)

[dete]

Great point! Thanks for reporting it, @pauliax!

Please see #13 for some info on how we're planning to replace these checks, based on a Gitter suggestion from @Arachnid.