Upgraded Q -> M from 45 [1657509796438]

[code423n4]

Judge has assessed an item in Issue #45 as Medium risk. The relevant finding follows:

[HickupHH3]

With regards to fees, we have the following possibilities:

• Put option exercised: No fee deducted, whole strike transferred to exerciser
• Put option expired: Fee deducted from payout of short
• Call option exercised: Fee deducted from payout of short
• Call option expired: No fee deducted While this is probably intended like that, it would be good to document this behavior, because there are other possibilites. My initial assumption, before reading the code, was that there is also a fee deducted from the exerciser when a put option is exercised.

dup of #285