createMarketSale have nftContractAddress as argument

[ghettoaliens]

Hello, first of all thank you very much for contributing with a marketplace code that people can use as an example.

And secondly, i think that the createMarketSale would have to get the contract address directly from the mapping array marketItemIdToMarketItem not as a function argument.

Because it could allow an external user to shop a token through a different contract address, not the address of the market item.

[Markkop]

Hey, @ghettoaliens! You're right, this improvement would give this contract greater versatility.
I might add this feature when I have time, but would you like to open a Pull Request with it?