CH12: s/Smores signature/Foocoin/

"Smore" sounds like "Schnorr", which could be confusing.  Also, we
have upgraded signatures now without a soft fork, so the example is
confusing.  Although we could add another coin with a soft fork (sort
of), it seems a lot less likely to me, so I think it's a better cadidate
for this section.

ch10.asciidoc

@@ -2214,15 +2214,14 @@ image::images/mbc2_1009.png[A blockchain with forks]
 Later, however, at block height 6, a hard fork occurs. Let's assume that
 a new implementation of the client is released with a change in the
 consensus rules. Starting on block height 7, miners running this new
-implementation will accept a new type of digital signature, let's call
-it a "Smores" signature, that is not ECDSA based. Immediately after, a
+implementation will accept a new type of bitcoin, let's call
+it a "foocoin". Immediately after, a
 node running the new implementation creates a transaction that contains
-a Smores signature and a miner with the updated software mines block 7b
+a foocoin and a miner with the updated software mines block 7b
 containing this transaction.
 
-Any node or miner that has not upgraded the software to validate Smores
 signatures is now unable to process block 7b. From their perspective,
-both the transaction that contained a Smores signature and block 7b that
+both the transaction that contained a Foo signature and block 7b that
 contained that transaction are invalid, because they are evaluating them
 based upon the old consensus rules. These nodes will reject the
 transaction and the block and will not propagate them. Any miners that
@@ -2232,12 +2231,12 @@ the old rules may not even receive block 7b if all the nodes they are
 connected to are also obeying the old rules and therefore not
 propagating the block. Eventually, they will be able to mine block 7a,
 which is valid under the old rules and does not contain any transactions
-with Smores signatures.
+with foocoins.
 
 The two chains continue to diverge from this point. Miners on the "b"
-chain will continue to accept and mine transactions containing Smores
-signatures, while miners on the "a" chain will continue to ignore these
-transactions. Even if block 8b does not contain any Smores-signed
+chain will continue to accept and mine transactions containing foocoins,
+while miners on the "a" chain will continue to ignore these
+transactions. Even if block 8b does not contain any foocoin
 transactions, the miners on the "a" chain cannot process it. To them it
 appears to be an invalid block, as its parent "7b" is not recognized as a
 valid block.