Confusing comment in smallerThan implementation

[josojo]

From Lasse:

For smallerThan in IterableOrderedOrderSet.sol there seem to be a mismatch between comment and the implementation, the comment says that it is ordered by: price, sellAmount and then userId, but from the implementation, it looks at the priceNumerator after the price.

While technically everything is correct, as we are sorting buy sellAmount and buyAmount (in this case of the code, we have: sellAmountLeft < sellAmountRight, if and only if buyAmountLeft < buyAmountRight) this comment is still confusing and should be corrected.