.env.sample: Update with new seller Coinbase API keys
.env.sample: Update with new seller Coinbase API keys

Need a second set of API keys for another user on Coinbase (the seller
in the transaction). It's a hack, okay, no OAuth here.

Using these we can send Bitcoins from the seller to the buyer as a proof
of concept for ownership transferral of the house.

teddywing/New-House-on-the-Block,teddywing/New-House-on-the-Block