[ ] Price: 1 LINK Use LINK's transferAndCall to do this
[ ] Only allow a purchase if the calling address has enough LINK
[ ] Should we only enforce the rank on purchase, or for every transfer? For every transfer would be pretty restrictive, but would make the NFTs more elite. But, that could get rid of secondary markets and possibly be difficult for LINK marines to deal with. What if they want to send their proof of rank to another wallet that has no LINK? I'll have to think about this one, maybe ask around a bit
[ ] I really like how Proof of Rank sounds...can we fit this into the name somehow?